docs: update contribution document

Author: streamtw

docs/contribution.md

@@ -9,5 +9,6 @@
     make init
     ```
 1. Edit codes in `vendor/unisharp/laravel-filemanager`
-1. Push your changes to your fork.
+1. Commit and follow rules in [Conventional Commits](https://www.conventionalcommits.org/).
+1. Push your changes to a new branch other than `master`. Good branch name might be like: `feature/add-pagination`, `fix/file-not-displayed`.
 1. Send a pull request to [unisharp/laravel-filemanager](https://github.com/UniSharp/laravel-filemanager).