Update dependency css-loader to v7

Author: renovate[bot]

package-lock.json

@@ -43,7 +43,7 @@
     "babel-loader": "8.4.1",
     "babel-plugin-transform-class-properties": "6.24.1",
     "copy-webpack-plugin": "5.1.2",
-    "css-loader": "5.2.7",
+    "css-loader": "7.1.2",
     "eslint": "5.16.0",
     "eslint-config-airbnb-base": "13.2.0",
     "eslint-loader": "2.2.1",