Bump postcss-cli from 6.1.3 to 7.1.0 (#1219)

Bumps [postcss-cli](https://github.com/postcss/postcss-cli) from 6.1.3 to 7.1.0.
- [Release notes](https://github.com/postcss/postcss-cli/releases)
- [Changelog](https://github.com/postcss/postcss-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss-cli/compare/6.1.3...7.1.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -92,7 +92,7 @@
     "moment": "^2.24.0",
     "node-sass": "^4.13.1",
     "npm-run-all": "^4.1.5",
-    "postcss-cli": "^6.1.3",
+    "postcss-cli": "^7.1.0",
     "prop-types": "^15.7.2",
     "qs": "^6.9.1",
     "react": "^16.12.0",