Animation.{effect|finished|ready} ship in Firefox 63 (#2650)
Animation.{effect|finished|ready} ship in Firefox 63 (#2650)

* Bug 1476158: Enable more of Animation interface
Add indications that Animation.ready, .finished, and
.effect are now enabled by default in Firefox 63.

chrisdavidmills/browser-compat-data,teoli2003/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data