Add .YAML-tmTheme as well

Author: mjbvz

.vscode/settings.json

@@ -3,6 +3,7 @@
     "editor.insertSpaces": true,
     "files.associations": {
         "*.YAML-tmLanguage": "yaml",
-        "*.YAML-tmPreferences": "yaml"
+        "*.YAML-tmPreferences": "yaml",
+        "*.YAML-tmTheme": "yaml"
     }
 }