chore: add dep on plugin

Author: ascorbic

demos/middleware/package.json

@@ -14,6 +14,7 @@
     "react-dom": "18.0.0"
   },
   "devDependencies": {
+    "@netlify/plugin-nextjs": "*",
     "@types/fs-extra": "^9.0.13",
     "@types/jest": "^27.4.1",
     "@types/node": "^17.0.25",

demos/server-components/package.json

@@ -16,6 +16,7 @@
     "react-dom": "^18.0.0"
   },
   "devDependencies": {
+    "@netlify/plugin-nextjs": "*",
     "@types/fs-extra": "^9.0.13",
     "@types/jest": "^27.4.1",
     "@types/node": "^17.0.25",