Librsvg moves to Gitlab

- gnome, librsvg

Librsvg now lives in GNOME's Gitlab instance. You can access it here.

Gitlab allows workflows similar to Github: you can create an account there, fork the librsvg repository, file bug reports, create merge requests... Hopefully this will make it nicer for contributors.

In the meantime, feel free to take a look!

This is a huge improvement for GNOME's development infrastructure. Thanks to Carlos Soriano, Andrea Veri, Philip Chimento, Alberto Ruiz, and all the people that made the move to Gitlab possible.