build(deps-dev): bump markdown-exec from 1.8.0 to 1.8.1

Bumps [markdown-exec](https://github.com/pawamoy/markdown-exec) from 1.8.0 to 1.8.1.
- [Release notes](https://github.com/pawamoy/markdown-exec/releases)
- [Changelog](https://github.com/pawamoy/markdown-exec/blob/main/CHANGELOG.md)
- [Commits](pawamoy/markdown-exec@1.8.0...1.8.1)

---
updated-dependencies:
- dependency-name: markdown-exec
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>