docs: Add more new docs content (#8874)
* add Getting Started page
* add Styling guide
* remove RAC imports from S2 docs examples
* add Migration page
* update links in Release Notes
* lint
* add index page
* lint
* fix mobile nav in dark mode
* add missing S2 component descriptions to JSDoc
* add No Results state for Icons and Illustrations search
* Add note to Illustration docs about pipeline name
* add coming soon pages for S2 Collections, Drag and Drop, and Selection
* rename S2 guide pages for better slugs
* git casing fix
* add version badge to S2 Toast docs
* fix todo link
* add Internationalized docs
* use BetaApp icon for Beta bage
* fix Icons and Illustrations search items
* improve RAC Button example
* fix UserCard props type
* make S2 style macro supported CSS properties list responsive
* enable horizontal scrolling BundlerSwitcher control
* lint
* fix 'Esc' keyboard listener
* add README.md for @react-spectrum/mcp
* have mcp server load markdown docs from CDN
* fix search menu background
* lint
