docs: RAC Toast docs for new docs site (#9219)
* add toast starter for vanilla css
* update to use tint and other color vars
* tailwind example
* fix centering
* toast docs rough draft
* split out toast animation code
* im dumb, fix animation
* double check colors
* update to get controls working and copy changes
* fix animation break due to multiple toast regions
* fix flicker
* review comments
