fix: update hierarchy to include Toc

src/content/editor/extensions/custom-extensions/extend-existing.mdx

@@ -36,13 +36,13 @@ new Editor({
 
 The same applies to every aspect of an existing extension, except to the name. Let’s look at all the things that you can change through the extend method. We focus on one aspect in every example, but you can combine all those examples and change multiple aspects in one `extend()` call too.
 
-### Name
+## Name
 
 The extension name is used in a whole lot of places and changing it isn’t too easy. If you want to change the name of an existing extension, you can copy the whole extension and change the name in all occurrences.
 
 The extension name is also part of the JSON. If you [store your content as JSON](/guides/output-json-html#option-1-json), you need to change the name there too.
 
-### Priority
+## Priority
 
 The priority defines the order in which extensions are registered. The default priority is `100`, that’s what most extension have. Extensions with a higher priority will be loaded earlier.
 
@@ -56,15 +56,15 @@ const CustomLink = Link.extend({
 
 The order in which extensions are loaded influences two things:
 
-1. #### Plugin order
+1. ### Plugin order
 
 ProseMirror plugins of extensions with a higher priority will run first.
 
-2. #### Schema order
+2. ### Schema order
 
 The [`Link`](/editor/extensions/marks/link) mark for example has a higher priority, which means it will be rendered as `<a href="…"><strong>Example</strong></a>` instead of `<strong><a href="…">Example</a></strong>`.
 
-### Settings
+## Settings
 
 All settings can be configured through the extension anyway, but if you want to change the default settings, for example to provide a library on top of Tiptap for other developers, you can do it like this:
 
@@ -81,7 +81,7 @@ const CustomHeading = Heading.extend({
 })
 ```
 
-### Storage
+## Storage
 
 At some point you probably want to save some data within your extension instance. This data is mutable. You can access it within the extension under `this.storage`.
 
@@ -113,7 +113,7 @@ const editor = new Editor({
 const awesomeness = editor.storage.customExtension.awesomeness
 ```
 
-### Schema
+## Schema
 
 Tiptap works with a strict schema, which configures how the content can be structured, nested, how it behaves and many more things. You [can change all aspects of the schema](/editor/core-concepts/schema) for existing extensions. Let’s walk through a few common use cases.
 
@@ -141,7 +141,7 @@ const CustomParagraph = Paragraph.extend({
 
 That’s just two tiny examples, but [the underlying ProseMirror schema](https://prosemirror.net/docs/ref/#model.SchemaSpec) is really powerful.
 
-### Attributes
+## Attributes
 
 You can use attributes to store additional information in the content. Let’s say you want to extend the default `Paragraph` node to have different colors:
 
@@ -217,7 +217,7 @@ const CustomParagraph = Paragraph.extend({
 
 You can completely disable the rendering of attributes with `rendered: false`.
 
-#### Extend existing attributes
+### Extend existing attributes
 
 If you want to add an attribute to an extension and keep existing attributes, you can access them through `this.parent()`.
 
@@ -236,7 +236,7 @@ const CustomTableCell = TableCell.extend({
 })
 ```
 
-### Global attributes
+## Global attributes
 
 Attributes can be applied to multiple extensions at once. That’s useful for text alignment, line height, color, font family, and other styling related attributes.
 
@@ -267,7 +267,7 @@ const TextAlign = Extension.create({
 })
 ```
 
-### Render HTML
+## Render HTML
 
 With the `renderHTML` function you can control how an extension is rendered to HTML. We pass an attributes object to it, with all local attributes, global attributes, and configured CSS classes. Here is an example from the `Bold` extension:
 
@@ -299,7 +299,7 @@ renderHTML({ HTMLAttributes }) {
 },
 ```
 
-### Parse HTML
+## Parse HTML
 
 The `parseHTML()` function tries to load the editor document from HTML. The function gets the HTML DOM element passed as a parameter, and is expected to return an object with attributes and their values. Here is a simplified example from the [`Bold`](/editor/extensions/marks/bold) mark:
 
@@ -344,7 +344,7 @@ You are wondering what’s that `&& null` doing? [ProseMirror expects `null` or
 
 [Pass `priority` to a rule](https://prosemirror.net/docs/ref/version/0.18.0.html#model.ParseRule.priority) to resolve conflicts with other extensions, for example if you build a custom extension which looks for paragraphs with a class attribute, but you already use the default paragraph extension.
 
-#### Using getAttrs
+### Using getAttrs
 
 The `getAttrs` function you’ve probably noticed in the example has two purposes:
 
@@ -384,7 +384,7 @@ addAttributes() {
 
 Read more about `getAttrs` and all other `ParseRule` properties in the [ProseMirror reference](https://prosemirror.net/docs/ref/#model.ParseRule).
 
-### Commands
+## Commands
 
 ```js
 import Paragraph from '@tiptap/extension-paragraph'
@@ -406,7 +406,7 @@ const CustomParagraph = Paragraph.extend({
   To access other commands inside `addCommands` use the `commands` parameter that’s passed to it.
 </Callout>
 
-### Keyboard shortcuts
+## Keyboard shortcuts
 
 Most core extensions come with sensible keyboard shortcut defaults. Depending on what you want to build, you’ll likely want to change them though. With the `addKeyboardShortcuts()` method you can overwrite the predefined shortcut map:
 
@@ -423,7 +423,7 @@ const CustomBulletList = BulletList.extend({
 })
 ```
 
-### Input rules
+## Input rules
 
 With input rules you can define regular expressions to listen for user inputs. They are used for markdown shortcuts, or for example to convert text like `(c)` to a `©` (and many more) with the [`Typography`](/editor/extensions/functionality/typography) extension. Use the `markInputRule` helper function for marks, and the `nodeInputRule` for nodes.
 
@@ -452,7 +452,7 @@ const CustomStrike = Strike.extend({
 })
 ```
 
-### Paste rules
+## Paste rules
 
 Paste rules work like input rules (see above) do. But instead of listening to what the user types, they are applied to pasted content.
 
@@ -483,7 +483,7 @@ const CustomStrike = Strike.extend({
 })
 ```
 
-### Events
+## Events
 
 You can even move your [event listeners](/editor/api/events) to a separate extension. Here is an example with listeners for all events:
 
@@ -515,7 +515,7 @@ const CustomExtension = Extension.create({
 })
 ```
 
-### What’s available in this?
+## What’s available in this?
 
 Those extensions aren’t classes, but you still have a few important things available in `this` everywhere in the extension.
 
@@ -536,11 +536,11 @@ this.options
 this.parent
 ```
 
-### ProseMirror Plugins (Advanced)
+## ProseMirror Plugins (Advanced)
 
 After all, Tiptap is built on ProseMirror and ProseMirror has a pretty powerful plugin API, too. To access that directly, use `addProseMirrorPlugins()`.
 
-#### Existing plugins
+### Existing plugins
 
 You can wrap existing ProseMirror plugins in Tiptap extensions like shown in the example below.
 
@@ -557,7 +557,7 @@ const History = Extension.create({
 })
 ```
 
-#### Access the ProseMirror API
+### Access the ProseMirror API
 
 To hook into events, for example a click, double click or when content is pasted, you can pass [event handlers](https://prosemirror.net/docs/ref/#view.EditorProps) to `editorProps` on the [editor](/editor/api/events).
 
@@ -593,7 +593,7 @@ export const EventHandler = Extension.create({
 })
 ```
 
-### Node views (Advanced)
+## Node views (Advanced)
 
 For advanced use cases, where you need to execute JavaScript inside your nodes, for example to render a sophisticated interface around an image, you need to learn about node views.