Allow brackets in task lists

What does this MR do?

Allows opening brackets to be used at the beginning of task list items.

Are there points in the code the reviewer needs to double check?

Security check of the diff between the two versions of the NPM package. The diff should be small and easy to review.

Why was this MR needed?

• deckar01/task_list#4
• #37990 (closed)
• #45599 (closed)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug (added in vendor repo)
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • [ ] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• [ ] Internationalization required/considered
• [ ] End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #37990 (closed)

Closes #45599 (closed)

Closes #56083 (closed)