chore(deps): update dependency css-minimizer-webpack-plugin to v3 (#4075)

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

package.json

@@ -112,7 +112,7 @@
     "compare-versions": "^3.3.0",
     "cross-env": "^7.0.0",
     "css-loader": "^5.0.0",
-    "css-minimizer-webpack-plugin": "^2.0.0",
+    "css-minimizer-webpack-plugin": "^3.0.0",
     "deep-assign": "^3.0.0",
     "docsearch.js": "^2.6.3",
     "enquire-js": "^0.2.1",