Bump wagtail-markdown from 0.10.0 to 0.11.0

Bumps [wagtail-markdown](https://github.com/torchbox/wagtail-markdown) from 0.10.0 to 0.11.0.
- [Release notes](https://github.com/torchbox/wagtail-markdown/releases)
- [Changelog](https://github.com/torchbox/wagtail-markdown/blob/main/CHANGELOG.md)
- [Commits](torchbox/wagtail-markdown@v0.10.0...v0.11.0)

---
updated-dependencies:
- dependency-name: wagtail-markdown
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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