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>

vite.config.js

@@ -37,4 +37,13 @@ export default defineConfig({
     port: 5173,
     open: true,
   },
+  test: {
+    globals: true,
+    environment: 'jsdom',
+    setupFiles: './tests/setup.js',
+    coverage: {
+      reporter: ['text', 'html'],
+      exclude: ['node_modules/', 'dist/', 'tests/'],
+    },
+  },
 });