Feature Request: add polyfill for TextEncoder and TextDecoder

[lpd-au]

What

Add a polyfill for TextEncoder and TextDecoder capable of encoding and decoding UTF-8.

Details

IE11 and EdgeHTML do not have support for the TextEncoder.prototype.encode and TextDecoder.prototype.decode apis. Native implementations of TextEncoder must only encode to UTF-8 but TextDecoder may support other encodings, however it is imo rare to use any other in practice given it's not reversible, so it would be sufficient to throw a RangeError when constructing a TextDecoder for any other encoding.

My use case for this polyfill is in combination with websockets. Websockets support a text and binary mode, and I would like to use this api to decode strings transmitted within the binary data (when aWebSocket.binaryType is set to arraybuffer), as well as send encoded strings back to the server.

Additional Information

MDN has a working polyfill for TextEncoder but not for TextDecoder. I submitted a request to that repo but was directed here instead: mdn/sprints#1508.

[JakeChampion]

This was added in #672 and released in v3.96.0