Update demo.scitokens.org

[jbasney]

The https://demo.scitokens.org/ site is an out-of-date clone of https://jwt.io/ that is customized to implement SciTokens Claims and SciTokens Verification. The source is https://github.com/scitokens/scitokens-heroku which is a fork of https://github.com/jsonwebtoken/jsonwebtoken.github.io.

Tasks include:

1. Merge in the latest code from https://github.com/jsonwebtoken/jsonwebtoken.github.io.
2. Add support for additional "Algorithm" values from https://jwt.io/.
3. Add support for additional verification checks (e.g., "iss check" and "typ check") from https://jwt.io/.

I think it's all in Javascript.

[jbasney]

See also related issue #5