implement base64url in Buffer

[huseeiin]

Environment

latest node and unenv

Reproduction

Buffer.from('hello').toString('base64url')

Describe the bug

base64url is not implemented

Additional context

base64url is just base64.replaceAll("+", "-").replaceAll("/", "_").replace("==", "")

there's feross/buffer#314 but the author is not proving it

Logs

[huseeiin]

you can also use deno's browser-compatible polyfills for node.js builtins: https://deno.land/std@0.177.0/node/internal/buffer.mjs?source

[pi0]

Do you mind to drop a PR?

Deno implementation is good, you can use this also I converted it to b64url only + small changes.