.btn
* Docs: add explanation of the base `.btn` class and a callout reminding authors to at least define some focus styling if they intend to use it "naked" * Turn callout into a warning * Add initial heading * Tweak callout wording
* Bump version to 5.3.0-alpha1 * Dist * Add docs versions updates * Update note in homepage hero Co-authored-by: Mark Otto <markdotto@gmail.com>