Bump node-sass from 4.12.0 to 7.0.0

Bumps [node-sass](https://github.com/sass/node-sass) from 4.12.0 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](https://github.com/sass/node-sass/compare/v4.12.0...v7.0.0)

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

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

package.json

@@ -18,7 +18,7 @@
     "imagemin-webpack-plugin": "^1.4.4",
     "jshint": "^2.9.4",
     "mocha": "^3.4.1",
-    "node-sass": "^4.5.3",
+    "node-sass": "^7.0.0",
     "postcss-loader": "^2.0.5",
     "sass-loader": "^6.0.5",
     "style-loader": "^0.18.0",