feat: add Vitest and Playwright testing frameworks

Set up Vitest for unit/integration tests and Playwright for E2E tests; add configs, tests, and documentation

Co-authored-by: Moheeb Zara <[email protected]>

tsconfig.json

@@ -22,6 +22,6 @@
       "@/*": ["./*"]
     }
   },
-  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
-  "exclude": ["node_modules"]
+  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts", "vitest.setup.ts"],
+  "exclude": ["node_modules", "dist", "build"]
 }