docs(RAC): add tailwind starter for Disclosure and DisclosureGroup (#7166)
* add tailwind starter for Disclosure and DisclosureGroup
* fix focus ring border radius
* update disabled chevron style
* fix focus ring in group
* cleanup variants and styles
* fix text color
* fix padding
* move DisclosureGroup to it's own story
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Co-authored-by: Robert Snow <rsnow@adobe.com>
Co-authored-by: Daniel Lu <dl1644@gmail.com>