docs: an overview document for dart_frog_cli

[wamynobe]

Description

Honestly, I was very confused when I first learned how team uses mason cli and bundles, so I think we should guide other contributors when they want to know how the project is using bricks to generate bundles. and use these bundles to generate necessary files for each command in dart_frog_cli. For example, when I edited the server.dart file in dev_server_runner brick, even though I ran tool/generate_bundles.sh, there was no indication that I had to edit the path to the brick folder in there for the commands in the cli to actually work. In the end I was still able to find the answer myself but it would take time for others. If possible, an overview document would be recommended. Thank you team for such a great Dart project.

Requirements

• [ ] Requirements go here