* Use `sessionStorage` to remember the previous results of calls to `browserSupportsEmoji()` for 1 week.
* Optimize reading from canvas by supplying the `willReadFrequently` option for the 2D context.
* When `OffscreenCanvas` is available, offload `browserSupportsEmoji()` to a web worker to prevent blocking the main thread. This is of primary benefit to Safari which does not yet support `willReadFrequently`.
* Remove obsolete support for IE11 since promises are now utilized. Nevertheless, ES3 syntax is maintained and IE11 will simply short-circuit.
Props westonruter, dmsnell, peterwilsoncc, valterlorran, flixos90, spacedmonkey, joemcgill.
Fixes#58472.
Built from https://develop.svn.wordpress.org/trunk@56074
git-svn-id: http://core.svn.wordpress.org/trunk@55586 1a063a9b-81f0-0310-95a4-ce76da25c4cd
80abb55903