Bump cross-env from 6.0.3 to 7.0.0 (#202)

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.json

@@ -44,7 +44,7 @@
     "@types/react": "^16.9.9",
     "@types/react-dom": "^16.9.2",
     "@types/warning": "^3.0.0",
-    "cross-env": "^6.0.3",
+    "cross-env": "^7.0.0",
     "enzyme": "^3.10.0",
     "enzyme-adapter-react-16": "^1.15.1",
     "enzyme-to-json": "^3.4.3",