Bump commander from 4.1.1 to 6.1.0

Bumps [commander](https://github.com/tj/commander.js) from 4.1.1 to 6.1.0.
- [Release notes](https://github.com/tj/commander.js/releases)
- [Changelog](https://github.com/tj/commander.js/blob/master/CHANGELOG.md)
- [Commits](tj/commander.js@v4.1.1...v6.1.0)

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

Author: dependabot-preview[bot]

package.json

@@ -71,7 +71,7 @@
     "browserify-imgify": "^0.0.1",
     "chromedriver": "75.1.0",
     "clean-css-cli": "^4.3.0",
-    "commander": "^4.0.1",
+    "commander": "^6.1.0",
     "cross-env": "^7.0.2",
     "css-loader": "^3.2.0",
     "es3ify-loader": "^0.2.0",