(docs deps): Bump the remark group with 3 updates

Bumps the remark group with 3 updates: [remark-heading-gap](https://github.com/remarkjs/remark-heading-gap), [remark-textr](https://github.com/remarkjs/remark-textr) and [remark-validate-links](https://github.com/remarkjs/remark-validate-links).


Updates `remark-heading-gap` from 5.0.1 to 6.0.0
- [Release notes](https://github.com/remarkjs/remark-heading-gap/releases)
- [Commits](remarkjs/remark-heading-gap@5.0.1...6.0.0)

Updates `remark-textr` from 5.0.1 to 6.0.0
- [Release notes](https://github.com/remarkjs/remark-textr/releases)
- [Commits](remarkjs/remark-textr@5.0.1...6.0.0)

Updates `remark-validate-links` from 12.1.1 to 13.0.0
- [Release notes](https://github.com/remarkjs/remark-validate-links/releases)
- [Commits](remarkjs/remark-validate-links@12.1.1...13.0.0)

---
updated-dependencies:
- dependency-name: remark-heading-gap
  dependency-type: direct:development
  update-type: version-update:semver-major
  dependency-group: remark
- dependency-name: remark-textr
  dependency-type: direct:development
  update-type: version-update:semver-major
  dependency-group: remark
- dependency-name: remark-validate-links
  dependency-type: direct:development
  update-type: version-update:semver-major
  dependency-group: remark
...

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Author: dependabot[bot]