Update dependency gh-pages to v2

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
gh-pages	devDependencies	major	1.2.0 -> 2.0.1	source

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Release Notes

tschaub/gh-pages

### [`v2.0.1`](https://togithub.com/tschaub/gh-pages/blob/master/changelog.md#v201) [Compare Source](https://togithub.com/tschaub/gh-pages/compare/v2.0.0...v2.0.1) - [#​268](https://togithub.com/tschaub/gh-pages/pull/268) - Continue even if no git configured user. ### [`v2.0.0`](https://togithub.com/tschaub/gh-pages/blob/master/changelog.md#v200) [Compare Source](https://togithub.com/tschaub/gh-pages/compare/v1.2.0...v2.0.0) Breaking changes: - Requires Node 6 and above. If you require support for Node 4, stick with v1.2.0. - The git user for commits is determined by running `git config user.name` and `git config user.email` in the current working directory when `gh-pages` is run. Ideally, this is what you want. In v1, the git user was determined based on the `gh-pages` install directory. If the package was installed globally, the git user might not have been what you expected when running in a directory with a locally configured git user. - [#​264](https://togithub.com/tschaub/gh-pages/pull/264) - Better user handling (thanks [@​holloway](https://togithub.com/holloway) for getting this going and [@​nuklearfiziks](https://togithub.com/nuklearfiziks) and [@​paulirish](https://togithub.com/paulirish) for pushing it over the edge) - [#​263](https://togithub.com/tschaub/gh-pages/pull/263) - Infra: newer syntax and upgrade deps to latest stable versions ([@​AviVahl](https://togithub.com/AviVahl))

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