Separate contributions on forked and source repositories

[mzfr]

It would be nice if we can get a contribution of a user on forked repo separately this would give an idea of how much a person works on other repos and how much they work on their own projects.

This can include:

• All the issue opened by a user on forked repository
• All the pull requests made to forked repos.
• All the commits on forked repos

If you like then you can make this at a bigger level and instead of just showing one tab of contribution for the user you can show two tabs contribution on forks and contributions on sources or something better.

[lourot]

Thanks, we'll think about it 👍 It has similarities with some aspects of #34 that @brillout and I discussed offline.