Add WPT tests that test base64url characters for hashes and nonces

[dveditz]

The hash source allowed characters was expanded to include basee64url characters in #37, with explanatory text on how to perform hash matching in this case added later in 1ceea1b. Years later this led to a web compatibility problem in Firefox https://bugzilla.mozilla.org/show_bug.cgi?id=1785871

We need platform tests that use this syntax for both nonces and hashes.

[mozfreddyb]

My Firefox patch will introduce a new test for wpt. I will land in our repo "mozilla-central" and eventually it be upstreamed through our tooling. Follow the bug if you want to know more.

[mozfreddyb]

I believe this can be closed in favor of web-platform-tests/wpt#35601