fix: Support Deno 2

[justinmchase]

This change is needed to run in Deno 2.

1. Upgrade the djwt module to latest
2. The new version of djwt no longer uses god_crypto, therefore upgrade the code to use WebCrypto APIs to import the cert.
3. WebCrypto only supports pkcs8 but github exports pkcs1 certs by default.
4. Add documentation on how to convert the github cert into pkcs8 format.
5. I also added some code to extract the content of the cert into the right format whether or not you leave the header/footer in or not.

• Fixes This is broken in deno 2.0 #7
• Fixes Broken on Deno 1.13 #1

[justinmchase]

Also, for what its worth I've added this logic directly into my github-api module so if anyone wants to use that api then its already in it.