Bump cross-env from 6.0.3 to 7.0.0

Bumps [cross-env](https://github.com/kentcdodds/cross-env) from 6.0.3 to 7.0.0.
- [Release notes](https://github.com/kentcdodds/cross-env/releases)
- [Changelog](https://github.com/kentcdodds/cross-env/blob/master/CHANGELOG.md)
- [Commits](kentcdodds/cross-env@v6.0.3...v7.0.0)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -10,7 +10,7 @@
     "@fortawesome/react-fontawesome": "^0.1.8",
     "bootstrap": ">=4.4.1",
     "codemirror": "^5.51.0",
-    "cross-env": "^6.0.3",
+    "cross-env": "^7.0.0",
     "crypto-js": "^3.1.9-1",
     "firebase": "^7.7.0",
     "immutable": "^3.8.2",