Bump node-sass from 4.13.0 to 7.0.0

Bumps [node-sass](https://github.com/sass/node-sass) from 4.13.0 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@v4.13.0...v7.0.0)

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

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

Author: dependabot[bot]

package.json

@@ -51,7 +51,7 @@
     "gatsby-plugin-sharp": "^2.3.13",
     "gatsby-source-filesystem": "^2.1.46",
     "gatsby-transformer-sharp": "^2.3.12",
-    "node-sass": "^4.13.0",
+    "node-sass": "^7.0.0",
     "prettier": "^1.19.1",
     "react": "^16.12.0",
     "react-dom": "^16.12.0",