* Add a button to add properties (which lets you select node and property)
* Add ability to drag properties and drop them to the editor.
* Made the editor transient (not always visible on the bottom) since its not needed most of the time.
* Added the ability to pin the editor, in case dragging properties from other nodes is desired.
Initial implementation of the MultiplayerReplicationInterface and its
default implementation (SceneReplicationInterface).
New MultiplayerSpawner node helps dealing with instantiation of scenes
on remote peers (e.g. clients).
It supports both custom spawns via a `_spawn_custom` virtual function,
and optional auto-spawn of known scenes via a TypedArray<PackedScenes>
property.
New MultiplayerSynchornizer helps synchronizing states between the local
and remote peers, supports both sync and spawn properties and is
configured via a `SceneReplicationConfig` resource.
It can also sync via path (i.e. without being spawned by a
MultiplayerSpawner if both peers has it in tree, but will not send the
spawn state in that case, only the sync one.
