docs: fix playground link

Author: js2me

docs/introduction/playground.md

@@ -1,10 +1,10 @@
 # Playground  
 
-You can try it out in [CodeSandbox](https://codesandbox.io/s/v4kdvz?file=/src/App.tsx).
+You can try it out in [CodeSandbox](https://codesandbox.io/p/sandbox/nl8kzc).
 
-<iframe src="https://codesandbox.io/embed/v4kdvz?view=editor+%2B+preview&module=%2Fsrc%2FApp.tsx&hidenavigation=1"
+<iframe src="https://codesandbox.io/embed/nl8kzc?view=editor+%2B+preview&module=%2Fsrc%2Findex.tsx"
   style="width:100%; height: 500px; border:0; border-radius: 4px; overflow:hidden;"
-  title="mobx-view-model-approach"
+  title="mobx-view-model-example"
   allow="accelerometer; ambient-light-sensor; camera; encrypted-media; geolocation; gyroscope; hid; microphone; midi; payment; usb; vr; xr-spatial-tracking"
   sandbox="allow-forms allow-modals allow-popups allow-presentation allow-same-origin allow-scripts"
 ></iframe>