Bump node-sass from 4.12.0 to 4.13.1

Bumps [node-sass](https://github.com/sass/node-sass) from 4.12.0 to 4.13.1.
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sass/node-sass/compare/v4.12.0...v4.13.1)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -43,7 +43,7 @@
     "html-webpack-plugin": "^3.2.0",
     "mini-css-extract-plugin": "^0.4.4",
     "mocha": "^5.2.0",
-    "node-sass": "4.12.0",
+    "node-sass": "4.13.1",
     "redux-devtools": "^3.4.0",
     "sass-loader": "^7.1.0",
     "standard": "^12.0.1",