Bump ssb-markdown from 6.0.4 to 6.0.7
Bump ssb-markdown from 6.0.4 to 6.0.7

Bumps [ssb-markdown](https://github.com/ssbc/ssb-markdown) from 6.0.4 to 6.0.7.
- [Release notes](https://github.com/ssbc/ssb-markdown/releases)
- [Commits](https://github.com/ssbc/ssb-markdown/compare/v6.0.4...v6.0.7)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
ssbc/patchwork,ssbc/patchwork