Add match_label API

[BimDav]

https://heroiclabs.com/docs/nakama/concepts/multiplayer/authoritative/#match-label

Listing matches is possible with the Godot API, as well as query filters on the match label, but it is not possible to set the match label as indicated in the above link.

Would it be possible to add it to the Godot API, either at match creation or later on, by the host?