Add dep @types/webpack

Workaround for vercel/next.js#16219

package.json

@@ -71,6 +71,7 @@
     "@types/react": "16.9.46",
     "@types/react-dom": "16.9.8",
     "@types/suncalc": "1.8.0",
+    "@types/webpack": "4.41.21",
     "@types/webpack-env": "1.15.2",
     "@typescript-eslint/eslint-plugin": "3.9.0",
     "@typescript-eslint/parser": "3.9.0",