refactor: bump node-sass from 6.0.1 to 7.0.0 (#2037)

Author: dependabot[bot]

package-lock.json

@@ -102,7 +102,7 @@
     "jest": "24.8.0",
     "madge": "5.0.1",
     "marked": "4.0.10",
-    "node-sass": "6.0.1",
+    "node-sass": "7.0.0",
     "null-loader": "4.0.1",
     "path-to-regexp": "3.2.0",
     "puppeteer": "3.0.0",