Gsom Loader

A threaded async loader for Godot resources.
Loads a resource in another thread and emits signals.

There is a singleton `GsomLoader` - a concurrent loader.
And it is possible to create any number of queued loaders - `GsomLoadQueue`. Both have similar APIs.

```
func _ready() -> void:
GsomLoader.finished_load.connect(_handleResource)
GsomLoader.changed_progress.connect(_handleProgress)
GsomLoader.failed_load.connect(_handleFail)

func _load() -> void:
GsomLoader.load_async("res://test.tscn")
```

See GitHub readme or the root example.gd for more details.