Docs/prepare 6.9 (#117)

* Docs refactor in prepartion for WordPress 6.9

Moved all PHP related docs to the php-api.md
Created new README.md file with correct doc ordering
Removed doc file numbering
Updating main repo README.md doc links

* Updating hooks

Adding reference for abilities_api_init

Moving hook registration in code examples above callback function for better readability

* Adding other category functions to PHP API

* Update README.md with direct link to docs README

* Adding ability_class information and example (#122)

* Adding ability_class information and example

* Adding contributing docs to Documenation section in the readme

* Fixing outdated link

* PR review updates

* Adding REST API docs updates from #120

* JavaScript client updates from #120

Co-authored-by: jonathanbossenger <psykro@git.wordpress.org>
Co-authored-by: gziolo <gziolo@git.wordpress.org>
Co-authored-by: aaronware <aware@git.wordpress.org>
Co-authored-by: galatanovidiu <ovidiu-galatan@git.wordpress.org>

Author: 5 people

README.md

@@ -18,16 +18,10 @@
 3. **Security‑first** - explicit permissions determine who/what may invoke an ability.
 4. **Gradual adoption** - ships first as a Composer package, migrates smoothly to core.
 
-## Developer Documentation
-
-- [Introduction](docs/1.intro.md)
-- [Getting Started](docs/2.getting-started.md)
-- [Registering Abilities](docs/3.registering-abilities.md)
-- [Using Abilities](docs/4.using-abilities.md)
-- [REST API Reference](docs/5.rest-api.md)
-- [Hooks](docs/6.hooks.md)
-- [JavaScript/TypeScript Client](docs/7.javascript-client.md)
-- [Contributing Guidelines](CONTRIBUTING.md)
+## Documentation
+
+- **[Developer docs](docs/README.md)**.
+- **[Contributing Guidelines](CONTRIBUTING.md)**.
 
 ## Inspiration