Add search for AUR packages by co-maintainer

[alerque]

The --maintainer flag is great for getting a list of packages I maintain so that I can do automated things like check out all of the package builds at once. However I also co-maintain a number of packages and it would be nice to be able to search for these as well. A --co-maintainer flag would be a nice addition.

[alerque]

It looks like adding this feature might be dependent on the upstream RPC interface supporting such a query. I've added a feature request regarding that.

[f2404]

You're right, that would require support from the RPC interface which seems to be missing.