feat: add CONTRIBUTING.md and update README with contribution guidelines; modify Vite config for headless browser testing

Co-authored-by: Copilot <copilot@github.com>

Author: Michael-Obele

CONTRIBUTING.md

@@ -0,0 +1,29 @@
+# Contributing
+
+Thanks for helping improve `sveltekit-openapi-generator`.
+
+## Before You Commit
+
+Run the test suite before committing changes:
+
+```bash
+bunx vitest run
+```
+
+If your change touches package output or published files, also run:
+
+```bash
+npm run package
+```
+
+## Recommended Workflow
+
+1. Make your change.
+2. Run `bunx vitest run`.
+3. Fix any failing tests.
+4. Run `npm run package` if the change affects built output.
+5. Commit once both checks are green.
+
+## Good PRs
+
+Keep changes focused, include tests for behavioral changes, and call out any generated artifacts that changed as a result of the update.

README.md

@@ -565,7 +565,9 @@ declare module 'virtual:openapi-spec' {
 
 ## 🤝 Contributing
 
-Contributions are welcome! Please feel free to submit a Pull Request.
+Contributions are welcome. Before committing, run `bunx vitest run` to make sure the unit and browser suites still pass.
+
+See [CONTRIBUTING.md](CONTRIBUTING.md) for the full workflow and checklist.
 
 <a name="license"></a>
 

vite.config.ts

@@ -42,7 +42,7 @@ export default defineConfig({
 					browser: {
 						enabled: true,
 						provider: 'playwright',
-						instances: [{ browser: 'chromium' }]
+						instances: [{ browser: 'chromium', headless: true }]
 					},
 					include: ['src/**/*.svelte.{test,spec}.{js,ts}'],
 					exclude: ['src/lib/server/**'],