Bump node-sass from 4.9.0 to 7.0.0 in /example

Bumps [node-sass](https://github.com/sass/node-sass) from 4.9.0 to 7.0.0.
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](sass/node-sass@v4.9.0...v7.0.0)

---
updated-dependencies:
- dependency-name: node-sass
  dependency-type: direct:production
...

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

Author: dependabot[bot]

example/package.json

@@ -22,7 +22,7 @@
     "html-webpack-plugin": "2.29.0",
     "jest": "22.4.2",
     "ml-classifier-ui": "file:../",
-    "node-sass": "^4.9.0",
+    "node-sass": "^7.0.0",
     "object-assign": "4.1.1",
     "postcss-flexbugs-fixes": "3.2.0",
     "postcss-loader": "2.0.8",