Make webpack-cli a dev-only dependency

We shouldn't need this in production. According to the [readme](https://www.npmjs.com/package/webpack-cli) it's only a dev dependency.

package.json

@@ -38,8 +38,7 @@
     "stimulus-flatpickr": "^1.4.0",
     "stimulus_reflex": "3.5.0-pre9",
     "tom-select": "^2.0.0",
-    "webpack": "~4",
-    "webpack-cli": "~3"
+    "webpack": "~4"
   },
   "devDependencies": {
     "husky": "^8.0.0",
@@ -51,6 +50,7 @@
     "karma-jasmine": "~0.3.8",
     "prettier": "2.7.1",
     "pretty-quick": "^3.1.3",
+    "webpack-cli": "~3",
     "webpack-dev-server": "~3"
   }
 }