Bump @babel/plugin-proposal-json-strings from 7.0.0 to 7.2.0

Bumps [@babel/plugin-proposal-json-strings](https://github.com/babel/babel) from 7.0.0 to 7.2.0.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](babel/babel@v7.0.0...v7.2.0)

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