chore(create_dart_frog): add "Powered by Dart Frog" badge to README (#256)

Author: felangel

bricks/create_dart_frog/__brick__/README.md

@@ -2,6 +2,7 @@
 
 [![style: very good analysis][very_good_analysis_badge]][very_good_analysis_link]
 [![License: MIT][license_badge]][license_link]
+[![Powered by Dart Frog](https://img.shields.io/endpoint?url=https://tinyurl.com/dartfrog-badge)](https://dartfrog.vgv.dev)
 
 An example application built with dart_frog