Bump prettier from 2.1.1 to 2.2.1 (#24)

Bumps [prettier](https://github.com/prettier/prettier) from 2.1.1 to 2.2.1.
- [Release notes](https://github.com/prettier/prettier/releases)
- [Changelog](https://github.com/prettier/prettier/blob/master/CHANGELOG.md)
- [Commits](prettier/prettier@2.1.1...2.2.1)

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