Created LoadingSimple Control

Created a simple Loading control to cover other UI controls, when
something is loading.

UI/Controls/loading_simple.gd

@@ -0,0 +1,16 @@
+@tool
+extends PanelContainer
+
+@export var rotation_speed: float = 1.0
+
+# Called when the node enters the scene tree for the first time.
+func _ready() -> void:
+	visibility_changed.connect(_on_visibility_changed)
+
+func _on_visibility_changed() -> void:
+	set_process(is_visible_in_tree())
+
+
+func _process(d: float) -> void:
+	%Spinner.rotation += d * TAU * rotation_speed
+	%Spinner.rotation = wrapf(%Spinner.rotation, 0, TAU)