chore(deps): update dependency css-loader to v6

Author: renovate[bot]

package-lock.json

@@ -59,7 +59,7 @@
     "codecov": "3.8.3",
     "commitlint-config-travi": "1.4.27",
     "cpy-cli": "4.2.0",
-    "css-loader": "5.2.7",
+    "css-loader": "6.8.0",
     "cz-conventional-changelog": "3.3.0",
     "enzyme": "3.11.0",
     "enzyme-adapter-react-16": "1.15.7",