chore(deps): update dependency webpack-cli to v4 (#4451)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

package.json

@@ -163,7 +163,7 @@
     "typescript": "^3.7.2",
     "unist-util-visit": "^1.4.0",
     "webpack": "^4.29.6",
-    "webpack-cli": "^3.2.3",
+    "webpack-cli": "^4.0.0",
     "webpack-dev-server": "^3.2.1"
   },
   "workspaces": {

packages/netlify-cms-editor-component-image/package.json

@@ -22,7 +22,7 @@
   "devDependencies": {
     "cross-env": "^7.0.0",
     "webpack": "^4.29.6",
-    "webpack-cli": "^3.2.3"
+    "webpack-cli": "^4.0.0"
   },
   "peerDependencies": {
     "react": "^16.8.4"