Allow custom definitions of "contribution"

[hut8]

I had difficulty determining what a "contribution" was beginning this. I definitely got all the ones that I considered contributions, but may have included too many. For example I think commenting on an issue counts as a contribution, but other people don't. So make a selection list where people can define which event types they consider to be "contributions" before querying.

[GaryJones]

A way to filter repos/events based on the type of contribution would definitely be handy i.e. find out which repos I actually had code committed to (directly via those I have write-access to, or via PR for those I don't), and not just opened a ticket at.

[joshjordan]

@GaryJones would gladly provide guidance and accept a PR for such functionality. That something you're interested in doing?

[GaryJones]

I've looked through the codebase, and right now, it's beyond me (using languages I'm not familiar with).