feat: added the new label comment_section in the groups

[PeterStaar-IBM]

To address comments and hidden text, we add a new group:

1. Things like slide comments, Word review comments, etc. should go into the furniture root and be put inside a group with new GroupLabel.COMMENT_SECTION
2. Optional: We can extend the type hierachy with a CommentItem, which additionally stores an author name and timestamp with the text.
3. We must add filter argument for group labels on the export functions (additional to DocItemLabels)

[mergify]

Merge Protections

Your pull request matches the following merge protections and will not be merged until they are valid.

🟢 Enforce conventional commit

Wonderful, this rule succeeded.

Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?(!)?: