Update rust config to add wgs/projects

I often see people do `r? rust-lang/wg-traits` or `r? rust-lang/wg-incr-comp` instead of `traits` or `incremental`. I just copied these groups from the expert map, but I think we should have at least aliases for some working groups or projects (by just making a new group with a singular member - a different group), or adding additional groups as necessary.