Update dependency css-loader to v3.4.0

Author: renovate-bot

package-lock.json

@@ -34,7 +34,7 @@
 		"@wordpress/postcss-themes": "2.2.0",
 		"@wordpress/scripts": "5.1.0",
 		"cross-env": "6.0.3",
-		"css-loader": "3.3.2",
+		"css-loader": "3.4.0",
 		"mini-css-extract-plugin": "0.8.1",
 		"node-sass": "4.13.0",
 		"postcss-loader": "3.0.0",