Mark animation* events supported since Firefox 5 (#15262)
Mark animation* events supported since Firefox 5 (#15262)

This is to match the AnimationEvent interface change:
https://github.com/mdn/browser-compat-data/pull/14174

CSS animations are mentinoed in the Firefox 5 release notes:
https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-us/firefox/5.0/releasenotes/

This has not been verified by testing.
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data