Support adding/removing metadata `remarks`

[Bronstrom]

Description

As a catalog author, I want to add/remove remarks in regard to metadata.

Acceptance Criteria

• A remark can be added
• A remark can be deleted
• Either one remark (no more than one) is visible or there is no remark at all.

Proposed Solution

If no remark exists, a button appears in its place with text like "+ Remark" or "Add Remark".

Additional Notes

No response

Implementation

• [ ] I can (or plan to) submit a pull request to implement this
• [ ] Implementing this may result in a breaking change

[Bronstrom]

Depends on #711