Bump node-sass from 4.9.2 to 7.0.0

Bumps [node-sass](https://github.com/sass/node-sass) from 4.9.2 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@v4.9.2...v7.0.0)

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

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

Author: dependabot[bot]

package.json

@@ -83,7 +83,7 @@
     "express": "^4.16.3",
     "gh-pages": "^1.2.0",
     "jest": "^24.9.0",
-    "node-sass": "^4.9.2",
+    "node-sass": "^7.0.0",
     "npm-run-all": "^4.1.3",
     "react": "^16.4.1",
     "react-dom": "^16.4.1",