README: description, contributing
Set up the usual project rules, following what wayland-protocols and wayland use.
Granting permissions is eased given this is mostly for documentation.
This assumes that !1 (merged) will land providing the license file.
Cc @swick, @vitalyp, @NaveenKumar, @hwentland - please make sure to subscribe to Issues and MRs in this project so I can stop mentioning you all explicitly.