Bumps [katex](https://github.com/KaTeX/KaTeX) from 0.12.0 to 0.13.0.
- [Release notes](https://github.com/KaTeX/KaTeX/releases)
- [Changelog](https://github.com/KaTeX/KaTeX/blob/master/CHANGELOG.md)
- [Commits](https://github.com/KaTeX/KaTeX/compare/v0.12.0...v0.13.0)
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