chore: add GUT test framework

addons/gut/.gutconfig.json

@@ -0,0 +1,23 @@
+{
+  "_post_run_script": "res://test/post_run_export_json.gd",
+
+  "include_subdirs": true,
+  "dirs": [
+    "res://test/unit/",
+    "res://test/integration/"
+  ],
+  "should_exit": true,
+  "log_level": 2,
+  "hide_orphans": false,
+
+  "should_exit_on_success": false,
+  "should_maximize": false,
+  "ignore_pause": true,
+  "double_strategy": "script_only",
+  "inner_class": "",
+  "disable_colors": false,
+  "compact_mode": true,
+  "gut_on_top": true,
+
+  "post_run_script":"res://test/gut_post_run.gd"
+}