build: mark plugins as dependencies

package.json

@@ -84,6 +84,7 @@
     "lodash.get": "^4.4.2",
     "lodash.set": "^4.3.2",
     "next": "^10.0.7",
+    "next-plugin-preval": "^1.2.1",
     "nodemailer": "^6.4.16",
     "nprogress": "^0.2.0",
     "postcss": "^8.2.1",
@@ -152,7 +153,6 @@
     "lint-staged": "^10.5.1",
     "msw": "^0.21.3",
     "netlify-cms-proxy-server": "^1.3.6",
-    "next-plugin-preval": "^1.2.1",
     "node-fetch": "^2.6.1",
     "prettier": "^2.2.1",
     "rimraf": "^3.0.2",