docs(contributing): add commit message convention guide

Added documentation explaining the conventional commit format used in this project.
This helps contributors understand the required commit message structure.

Author: Copilot

.github/COMMIT_CONVENTION.md

@@ -0,0 +1,41 @@
+# Commit Message Convention
+
+This project follows the [Conventional Commits](https://www.conventionalcommits.org/) specification.
+
+## Format
+
+```
+type(scope): subject
+
+body
+
+footer
+```
+
+## Types
+
+- `feat`: A new feature
+- `fix`: A bug fix
+- `docs`: Documentation changes
+- `style`: Code style changes (formatting, missing semi-colons, etc.)
+- `refactor`: Code refactoring
+- `perf`: Performance improvements
+- `test`: Adding or updating tests
+- `build`: Changes to build system or dependencies
+- `ci`: Changes to CI configuration
+- `chore`: Other changes that don't modify src or test files
+
+## Examples
+
+```
+docs(readme): add installation instructions
+
+feat(auth): implement JWT authentication
+
+fix(api): resolve null pointer exception in user endpoint
+```
+
+## Validation
+
+All commits are validated using commitlint with the conventional config.
+See `commitlint.config.js` for configuration details.