Add a way to discover /wayland-protocols/[IID] route

[PolyMeilex]

Now that we have a way to view gitlab MR protocols (#32) we need a way to advertise this to users.
Probably the best way to advertise this feature would be to implement a /wayland-protocols subpage that would list all open MRs.

GitLab API Quary similar to this one could be used for that

query {
  project(fullPath: "wayland/wayland-protocols") {
    mergeRequests(state: opened, first: 20) {
      count,
      nodes {
        iid
        title,
        diffStats { path },
      }
    }
  }
}