chore: add GUT test framework

addons/gut/scratch/make_doubled_thing.gd

@@ -0,0 +1,10 @@
+# Used with doubled_thing.gd.  This will create an instance of that to try and
+# find issues.  doubled_thing.gd has source from a doubled object.
+extends SceneTree
+
+func _init():
+    var DoubledThing = load('res://scratch/doubled_thing.gd')
+    print(DoubledThing)
+    var inst = DoubledThing.new()
+    print(inst)
+    quit()