docs: update and simplify all documentation (#39686)

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

docs/how-to-work-on-the-docs-theme.md

@@ -1,13 +1,11 @@
 # How to work on the docs theme
 
 > [!NOTE]
-> **You do not need to setup anything locally for working on the documentation content.**
+> A quick reminder that you do not need to setup anything for working on the content for the documentation site.
 >
 > To work on the contributing guidelines, you can edit or add files in the `docs` directory [available here](https://github.com/freeCodeCamp/freeCodeCamp/tree/master/docs). When your changes are merged, it will be made available automatically at the documentation site.
 
-## About the documentation site
-
-While you do not need to generate the documentation site locally, sometimes it may be required for instance if you are working on the site theme or a feature for the site.
+## Structure of the docs website
 
 The site is generated using [`docsify`](https://docsify.js.org), and served using GitHub pages.
 
@@ -16,8 +14,8 @@ Typically you would not need to change any configuration or build the site local
 - The homepage's source for this site is available in [`docs/index.html`](index.html).
 - We serve this file as a SPA using `docsify` and GitHub Pages.
 - The `docsify` script generates the content of `markdown` files in `docs` directory on demand.
-- The homepage is generated from the [`index.md`](index.md).
-- the sidebar navigation is generated from [`components/sidebar.md`](components/sidebar.md).
+- The homepage is generated from the [`_coverpage.md`](_coverpage.md).
+- the sidebar navigation is generated from [`_sidebar.md`](_sidebar.md).
 
 ## Serving the documentation site locally