Bump remark-frontmatter from 4.0.1 to 5.0.0 (#48)

Bumps [remark-frontmatter](https://github.com/remarkjs/remark-frontmatter) from 4.0.1 to 5.0.0.
- [Release notes](https://github.com/remarkjs/remark-frontmatter/releases)
- [Commits](remarkjs/remark-frontmatter@4.0.1...5.0.0)

---
updated-dependencies:
- dependency-name: remark-frontmatter
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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