Update dependency css-loader to v4

Author: renovate-bot

package-lock.json

@@ -62,7 +62,7 @@
     "@wordpress/block-library": "2.24.0",
     "babel-loader": "8.1.0",
     "browserify-transform-tools": "1.7.0",
-    "css-loader": "3.6.0",
+    "css-loader": "4.3.0",
     "cssnano": "4.1.10",
     "cypress": "5.2.0",
     "eliminate": "1.1.2",