Update for newer GitHub token format?

[kingthorin]

If https://github.com/dxa4481/truffleHogRegexes/blob/master/truffleHogRegexes/regexes.json really is the base rule set for TruffleHog as stated on: https://github.com/trufflesecurity/truffleHog#customizing, then it should have a new entry that accommodates updated GitHub tokens.

Per https://github.blog/changelog/2021-03-31-authentication-token-format-updates-are-generally-available/

It seems like the existing GitHub regex uses the right charset. However, it doesn’t account for the new prefixes or length up to 255.

[kingthorin]

I’m happy to open a PR if there’s agreement on this.

Edit: looks like someone already tackled this, https://github.com/dxa4481/truffleHogRegexes/pull/27/