Update dependency webpack-merge to v4.2.2

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
webpack-merge	dependencies	patch	4.2.1 -> 4.2.2

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Release Notes

survivejs/webpack-merge

### [`v4.2.2`](https://togithub.com/survivejs/webpack-merge/blob/master/CHANGELOG.md#​422--2019-08-27) [Compare Source](https://togithub.com/survivejs/webpack-merge/compare/v4.2.1...v4.2.2) ================= - Fix - Update minimum version of lodash to 4.17.15 in order to avoid `npm audit warning`. [#​116](https://togithub.com/survivejs/webpack-merge/issues/116) - Docs - Improve `merge.unique` documentation. [#​103](https://togithub.com/survivejs/webpack-merge/issues/103) - Docs - Add clear note about precedence. [#​115](https://togithub.com/survivejs/webpack-merge/issues/115)

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