Bump uglifyjs-webpack-plugin from 1.2.7 to 1.3.0

Bumps [uglifyjs-webpack-plugin](https://github.com/webpack-contrib/uglifyjs-webpack-plugin) from 1.2.7 to 1.3.0.
- [Release notes](https://github.com/webpack-contrib/uglifyjs-webpack-plugin/releases)
- [Changelog](https://github.com/webpack-contrib/uglifyjs-webpack-plugin/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/uglifyjs-webpack-plugin@v1.2.7...v1.3.0)

Author: dependabot-preview[bot]

package-lock.json

@@ -158,7 +158,7 @@
     "stylelint-config-standard": "16.0.0",
     "to-source": "3.1.3",
     "uglify-js": "3.6.0",
-    "uglifyjs-webpack-plugin": "1.2.7",
+    "uglifyjs-webpack-plugin": "1.3.0",
     "url-loader": "1.1.2",
     "webpack": "3.12.0",
     "webpack-bundle-size-analyzer": "3.0.0",