Automatically set heading level

[rg-wood]

Currently, we have to remember to set the heading level of each page to ensure it follows the correct document outline (i.e. h1/# in the README.md, h2/## in the section indexes). Instead, we should set the heading level automatically based on the following ordering:

1. Section indexes (index.md or README.md).
2. Section pages.
3. Handle sub-sections.

To support this, we should use the Obsidian markdown naming convention of putting the document title in the Markdown's file name, and not giving the file a main heading.