docs: Testing docs (#9164)
* add FAQ and other sections
* add section for creating custom components
* initial stab at extracting types from style macro
* testing sizing properties
* revert export of theme object since it was breaking inference
* adding more values
* reorg
* add the rest of the properties and double check them
* add more type links
* add mdn links for common types and specific css properties
* add relative links so basecolors and various dimension strings link back to the visual
* add descriptions to table and get rid of unessasary isRelative
* add short hand and condition tables
* add subpage for reference and advanced style macro section
* support subpage list under the ToC
* forgot to move last bit of content
* update FAQ, add mobile related pages, link from RAC styling
* fix mobile styling
* initial react aria testing docs
* pare down content for readability
* adding S2 testing docs
* add sample subpage content
* add style for blockquote
* add new test util docs to old website
* add examples to new docs
* clean up old code, no more switcher
* refactor test util content so it is in each page
* debug why subpage why failing
* move to subpages
* review comments
* fix build links?
* rename mdx file to fix all links
* small fixes
* move reference out of subpage and merge styling page
* make icons page lowercase and fix shorthands link
* whoops forgot to make git track the capitalization rename
* use isSubPage and update to detect parent link
* export only the type
* addressing feedback from quarry team
* update subpage back button logic
* add testing option back to mobile ToC
* fix bad merge
* review comments
* forgot to add separate headers
* bring back bullet points
