implement base64url in buffer by switching to js-base64

[huseeiin]

fixes #462

[pi0]

@huseeiin any specific reason you haven't gone with Deno stdlib implementation as your original idea? checking, it seems this lib has extra polyfills for legacy env without atob support which we probably don't need that concern here.

[huseeiin]

@huseeiin any specific reason you haven't gone with Deno stdlib implementation as your original idea? checking, it seems this lib has extra polyfills for legacy env without atob support which we probably don't need that concern here.

i will use the deno stdlib version if you want, i support that idea too!