fix(deps): update dependency file-loader to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
file-loader	dependencies	major	3.0.1 -> 4.0.0

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Release Notes

webpack-contrib/file-loader

### [`v4.0.0`](https://togithub.com/webpack-contrib/file-loader/blob/master/CHANGELOG.md#​400httpsgithubcomwebpack-contribfile-loadercomparev301v400-2019-06-05) [Compare Source](https://togithub.com/webpack-contrib/file-loader/compare/v3.0.1...v4.0.0) ##### chore - **deps:** update ([#​333](https://togithub.com/webpack-contrib/file-loader/issues/333)) ([0d2f9b8](https://togithub.com/webpack-contrib/file-loader/commit/0d2f9b8)) ##### BREAKING CHANGES - **deps:** minimum required nodejs version is `8.9.0`

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