Bump @tiptap/pm from 2.6.6 to 2.8.0 (#7)

Bumps [@tiptap/pm](https://github.com/ueberdosis/tiptap/tree/HEAD/packages/pm) from 2.6.6 to 2.8.0.
- [Release notes](https://github.com/ueberdosis/tiptap/releases)
- [Changelog](https://github.com/ueberdosis/tiptap/blob/develop/packages/pm/CHANGELOG.md)
- [Commits](https://github.com/ueberdosis/tiptap/commits/@tiptap/[email protected]/packages/pm)

---
updated-dependencies:
- dependency-name: "@tiptap/pm"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>