chore(ci): use corepack to pin pnpm version (#858)

This will pin the version of pnpm to make sure we're all use the same
version and avoid unncessary lockfile changes.

```
corepack use pnpm@latest
```

package.json

@@ -2,6 +2,10 @@
   "name": "examples",
   "license": "MIT",
   "private": true,
+  "packageManager": "[email protected]+sha256.2df78e65d433d7693b9d3fbdaf431b2d96bb4f96a2ffecd51a50efe16e50a6a8",
+  "engines": {
+    "pnpm": "8.14.1"
+  },
   "scripts": {
     "lint-staged": "lint-staged",
     "new-example": "plop example",