Bump cross-env from 5.1.3 to 7.0.2 (#91)

Bumps [cross-env](https://github.com/kentcdodds/cross-env) from 5.1.3 to 7.0.2.
- [Release notes](https://github.com/kentcdodds/cross-env/releases)
- [Changelog](https://github.com/kentcdodds/cross-env/blob/master/CHANGELOG.md)
- [Commits](kentcdodds/cross-env@v5.1.3...v7.0.2)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

package-lock.json

@@ -53,7 +53,7 @@
     "babel-plugin-transform-flow-strip-types": "^6.22.0",
     "babel-preset-es2015": "^6.24.1",
     "babel-preset-power-assert": "^2.0.0",
-    "cross-env": "^5.1.3",
+    "cross-env": "^7.0.2",
     "css-loader": "^3.2.0",
     "eslint": "^4.18.2",
     "eslint-plugin-flowtype": "^2.46.1",