doc: Uint8Array support in Buffer functions

Buffer.from / new Buffer accept Uint8Array

Fixes: https://github.com/nodejs/node/issues/14118

Backport-PR-URL: https://github.com/nodejs/node/pull/21590
PR-URL: https://github.com/nodejs/node/pull/19949


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>