set pnpm version in package.json to make github CI work

Author: waveproc

package.json

@@ -15,6 +15,8 @@
     "astro": "5.13.4",
     "astro-expressive-code": "0.41.3",
     "boxicons": "^2.1.4",
+    "sharp": "^0.34.3",
     "tailwindcss": "4.1.12"
-  }
-}
+  },
+  "packageManager": "[email protected]"
+}