docs: color scheme switcher (#9403)
* add settings dialog for color scheme, package manager, styling solution, and css theme
* add icons for color scheme
* fix RAC examples to use correct color scheme
* add color scheme options to markdown menu
* typescript
* use color scheme toggle in Header (for React Spectrum)
* fix lint
* cleanup
* fix search menu background color
* add switcher to mobile header
* remove cursor-pointer
* add divider
* add transition to icon change
