chore: add frappe ui playground to gitignore

Author: ruchamahabal

.gitignore

@@ -8,6 +8,8 @@ __pycache__
 studio/docs/current
 studio/public/frontend
 studio/www/studio.html
+# for testing frappe-ui
+frappeui_playground
 # default renderer auto-generated by studio
 studio/templates/generators/studio_renderer.html
 studio/public/app_builds