Feature Request - Add additional metrics

[Rucknar]

Current metrics are basic, add in at least:

• Last commit timestamp
• Issues closed (we already have open)
• Downloads
• Releases

[cweagans]

I started diving into getting Release/Downloads info into the exporter, but it looks like the way everything is built right now assumes that a Repository is really the only thing that the exporter should care about. Adding Release data seems like a pretty substantial refactor. If you want, I can go ahead with it, but I figured I'd ask first to make sure that a large PR wouldn't be rejected here.

[Rucknar]

It was originally built to cover just repositories I guess. See no reason to limit it though and would welcome a PR, I’m on leave at the mo but happy to code review when back.

[cweagans]

👍