build(deps-dev): bump node-sass from 5.0.0 to 6.0.0 in /frontend (#934)

Bumps [node-sass](https://github.com/sass/node-sass) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](sass/node-sass@v5.0.0...v6.0.0)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

frontend/package-lock.json

@@ -40,7 +40,7 @@
     "file-loader": "^6.0.0",
     "html-webpack-plugin": "^5.3.1",
     "mini-css-extract-plugin": "^1.3.9",
-    "node-sass": "^5.0.0",
+    "node-sass": "^6.0.0",
     "prettier": "1.19.1",
     "sass-loader": "^11.0.1",
     "standard": "^16.0.1",