Feature: Dynamic web stories from backend

[amovar18]

Description

This PR aims to build dynamic stories from the backend response.

Relevant Technical Choices

• Fetch the set of stories from the backend parse the response and generate a single story object that looks like the following:

{
  heroImage: string;
  publisherLogo: string;
  publisherName: string;
  storyTitle: string;
  storyUrl: string;
}

• This PR also fetches the filters of Category, Author and Tags from API calls to the backend.

Testing Instructions

• Clone this branch.
• In the terminal run npm i && npm run build:ext.
• Now go to example.com and open the DevTools and open Privacy Sandbox tab.
• You should see a section in sidebar titled as Explorable Explanation with Web-Stories Icon.
• Click on the section. A set of stories with their hero image should be rendered on the main content.
• Clicking on the hero image will result in the story opening in a light box.

Additional Information:

The following things are to be done:

• Fetch tags from the backend.
• Add infinite scroll to the stories.

Screenshot/Screencast

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Checklist

• I have thoroughly tested this code to the best of my abilities.
• I have reviewed the code myself before requesting a review.
  - [ ] This code is covered by unit tests to verify that it works as intended.
• The QA of this PR is done by a member of the QA team (to be checked by QA).

Fixes #897

[mohdsayed]

@amovar18

1. Initially it shows only 4 stories with arrow down indicator however scrolling down doesn't work.

It works in vertical mode however the placement of arrow down doesn't look right.

2. Is it a requirement to load only 4 stories in the beginning?
   

3. When no stories are found, it should say that instead of showing empty screen
   

4. When more stories are loading, it should indicate that using some text or loader.

5. Is it possible to close the popup on esc button press?

[mohdsayed]

Some more improvements:

1. When there are no stories, down arrow should not appear.
2. Where there are no stories in search, arrow up should not appear.
3. When it's waiting for stories to load, it should show loader.
   

Recommendations:

• Arrow down can be clickable and should load more stories.
• Arrow up should scroll to the top.
• Increase initial stories count to at least 8 so that it doesn't show empty space and user has something to scroll.

[mohdsayed]

Needs few improvements.