build(deps-dev): bump uglifyjs-webpack-plugin from 1.3.0 to 2.2.0

Bumps [uglifyjs-webpack-plugin](https://github.com/webpack-contrib/uglifyjs-webpack-plugin) from 1.3.0 to 2.2.0.
- [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@v1.3.0...v2.2.0)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -54,7 +54,7 @@
     "typedoc": "^0.13.0",
     "typedoc-twilio-theme": "^1.0.0",
     "typescript": "^3.1.6",
-    "uglifyjs-webpack-plugin": "^1.2.7",
+    "uglifyjs-webpack-plugin": "^2.2.0",
     "webpack": "^4.25.1",
     "webpack-cli": "^3.1.2",
     "webpack-node-externals": "^1.7.2"