feat: Add testing infrastructure and documentation

- Set up Vitest for unit testing with jsdom
- Add test setup with Web Audio API and requestAnimationFrame mocks
- Create initial test suites for DOM and animations modules
- Add test scripts to package.json (test, test:ui, test:run, coverage)
- Update CI workflow to include test execution
- Create CONTRIBUTING.md with conventional commits guidelines
- Create SECURITY.md with security policy
- Update ESLint config to support test files
- All tests passing (8/8)

Co-authored-by: ZaneThePython <102631678+ZaneThePython@users.noreply.github.com>

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ on:
     branches: [ main ]
 
 jobs:
-  lint-and-build:
+  lint-test-build:
     runs-on: ubuntu-latest
     
     strategy:
@@ -33,6 +33,9 @@ jobs:
     - name: Check formatting
       run: npm run format:check
       
+    - name: Run tests
+      run: npm run test:run
+      
     - name: Build project
       run: npm run build