A transform stream that encodes strings into UTF-8 bytes.
See also:
https://nodejs.org/api/globals.html#class-textencoderstream
https://nodejs.org/api/webstreams.html#class-textencoderstream
new()
read onlyencoding:String
Always "utf-8".
"utf-8"
read onlyreadable:ReadableStream
read onlywritable:WritableStream