build(deps-dev): bump webpack-cli from 4.1.0 to 4.2.0 in /addon (#657)

Bumps [webpack-cli](https://github.com/webpack/webpack-cli) from 4.1.0 to 4.2.0.
- [Release notes](https://github.com/webpack/webpack-cli/releases)
- [Changelog](https://github.com/webpack/webpack-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-cli/compare/[email protected]@4.2.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

addon/package-lock.json

@@ -13,7 +13,7 @@
     "eslint-plugin-no-unsanitized": "^3.1.4",
     "web-ext": "^5.3.0",
     "webpack": "^4.44.2",
-    "webpack-cli": "^4.1.0"
+    "webpack-cli": "^4.2.0"
   },
   "scripts": {
     "lint": "eslint src/*.js",