chore: add build command

Author: ascorbic

package.json

@@ -14,7 +14,7 @@
     "format:check-fix:prettier": "run-e format:check:prettier format:fix:prettier",
     "format:check:prettier": "cross-env-shell prettier --check $npm_package_config_prettier",
     "format:fix:prettier": "cross-env-shell prettier --write $npm_package_config_prettier",
-    "build": "npm run -w @netlify/plugin-nextjs build",
+    "build": "npm run build -w packages/next -w packages/runtime",
     "postinstall": "run-s build install-husky",
     "install-husky": "if-env CI=1 || husky install node_modules/@netlify/eslint-config-node/.husky",
     "test": "run-s build:demo test:jest",