Bump webpack-merge from 4.2.2 to 5.0.9

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 4.2.2 to 5.0.9.
- [Release notes](https://github.com/survivejs/webpack-merge/releases)
- [Changelog](https://github.com/survivejs/webpack-merge/blob/master/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/compare/v4.2.2...v5.0.9)

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

package.json

@@ -107,7 +107,7 @@
 		"webpack": "^4.44.0",
 		"webpack-cli": "^3.3.12",
 		"webpack-dev-server": "^3.11.0",
-		"webpack-merge": "^4.2.2"
+		"webpack-merge": "^5.0.9"
 	},
 	"jest": {
 		"moduleFileExtensions": [