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>

package.json

@@ -7,6 +7,10 @@
     "dev": "vite",
     "build": "vite build",
     "preview": "vite preview",
+    "test": "vitest",
+    "test:ui": "vitest --ui",
+    "test:run": "vitest run",
+    "coverage": "vitest run --coverage",
     "lint": "eslint . --ext .js,.html",
     "lint:fix": "eslint . --ext .js,.html --fix",
     "format": "prettier --write \"**/*.{js,html,css,json,md}\"",
@@ -28,14 +32,17 @@
   },
   "homepage": "https://zane.org",
   "devDependencies": {
+    "@vitest/ui": "^4.0.8",
     "eslint": "^9.39.1",
     "eslint-config-prettier": "^10.1.8",
     "eslint-plugin-html": "^8.1.3",
     "imagemin": "^9.0.1",
     "imagemin-mozjpeg": "^10.0.0",
     "imagemin-pngquant": "^10.0.0",
+    "jsdom": "^27.1.0",
     "prettier": "^3.6.2",
     "terser": "^5.44.1",
-    "vite": "^7.2.2"
+    "vite": "^7.2.2",
+    "vitest": "^4.0.8"
   }
 }