docs: add contributing guidelines for commit messages

Author: yajra

CONTRIBUTING.md

@@ -5,6 +5,24 @@ Contributions are **welcome** and will be fully **credited**.
 We accept contributions via Pull Requests on [Github](https://github.com/yajra/laravel-datatables-export).
 
 
+## Commit messages — Conventional Commits (recommended)
+
+We follow the Conventional Commits specification for all commit messages to keep history clear and to allow automated changelog/release tooling.
+
+- Format: `<type>(optional-scope): <short-description>`
+- Examples:
+  - `feat: add export queue support`
+  - `fix(export): handle empty dataset exception`
+  - `chore(deps): bump phpunit to ^10.0`
+  - `docs: update README with contrib guidelines`
+
+Types we commonly use: `feat`, `fix`, `chore`, `docs`, `style`, `refactor`, `perf`, `test`, `build`, `ci`.
+
+This is a documentation-only guideline. There is no required tooling in the repository to enforce commit messages; contributors are asked to follow the format when writing commit messages. If you prefer to use local tooling (for example `commitlint` + `husky`) that's fine, but it's not required by the maintainers.
+
+If you run into issues or have questions about commit formatting, open an issue or drop a note in the PR — maintainers can help.
+
+
 ## Pull Requests
 
 - **[PSR-2 Coding Standard](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md)** - The easiest way to apply the conventions is to install [PHP Code Sniffer](http://pear.php.net/package/PHP_CodeSniffer).
@@ -16,4 +34,4 @@ We accept contributions via Pull Requests on [Github](https://github.com/yajra/l
 - **Send coherent history** - Make sure each individual commit in your pull request is meaningful. If you had to make multiple intermediate commits while developing, please squash them before submitting.
 
 
-**Happy coding**!
+**Happy coding**!