Better fix: Upgrade @codesandbox/sandpack-react to v2.20.0

- Upgraded from 2.13.5 to 2.20.0 which natively supports React 19

- Removed .npmrc workaround - no longer needed

- This is a proper solution instead of using legacy-peer-deps

Author: Mohamed-Hashem

.npmrc

@@ -27,7 +27,7 @@
   },
   "dependencies": {
     "@babel/types": "7.28.5",
-    "@codesandbox/sandpack-react": "2.13.5",
+    "@codesandbox/sandpack-react": "^2.20.0",
     "@docsearch/css": "^3.8.3",
     "@docsearch/react": "^3.8.3",
     "@headlessui/react": "^1.7.0",