Redesign Extensions TOC

[mikehoffms]

Rendered:
https://review.learn.microsoft.com/microsoft-edge/extensions-chromium/?branch=pr-en-us-2899

This PR might do the following, in the Extensions articles:

• Rework the TOC.
  • Procedure: Flatten TOC by removing buckets (parent nodes). Reorder articles in linear order, grouping articles that cover the same topic. Where there's a series of multiple articles covering a given topic, create a TOC bucket (parent node).
• Retitle articles, eg. starting with the differentiating key words.
• Normalize "add-on" vs. "extension".
• Normalize "store" vs. "website".

AB#47324498

[learn-build-service-prod]

Learn Build status updates of commit baceef0:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-edge/toc.yml	✅Succeeded	View

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel