Update dependency node-sass to v4.13.1

Author: renovate-bot

package-lock.json

@@ -29,7 +29,7 @@
     "html-webpack-plugin": "3.2.0",
     "istanbul-instrumenter-loader": "3.0.1",
     "istanbul-lib-coverage": "2.0.5",
-    "node-sass": "4.13.0",
+    "node-sass": "4.13.1",
     "nyc": "14.1.1",
     "sass": "1.24.4",
     "sass-loader": "7.3.1",