Bump node-sass from 4.0.0 to 4.13.1 in /examples/server rendering

Bumps [node-sass](https://github.com/sass/node-sass) from 4.0.0 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](sass/node-sass@v4.0.0...v4.13.1)

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

Author: dependabot[bot]

examples/server rendering/package.json

@@ -49,7 +49,7 @@
     "file-loader": "0.9.0",
     "html-webpack-plugin": "2.24.1",
     "json-loader": "0.5.4",
-    "node-sass": "4.0.0",
+    "node-sass": "4.13.1",
     "postcss-loader": "1.2.1",
     "replace": "0.3.0",
     "rimraf": "2.5.4",