Summary:
Implement a function to fetch all rubric assessments for a specific assignment.

What to implement:

• Function: list_assignment_rubric_assessments(course_id, assignment_id, ...)
• Endpoint: GET /api/v1/courses/:course_id/assignments/:assignment_id/rubric_assessments
• Optional params:
  • style (string; e.g., "full", "comments_only")
  • Pagination (as appropriate)
• Returns: List/dataframe of rubric assessment objects with associated metadata.

Design notes:

• Use consistent pagination and return conventions as other list_* methods.
• Document expected response and typical usage.
• Link Canvas API docs in Roxygen.
• Add to appropriate section in pkgdown.yml ("Rubrics" or "Assignments").

To update:

• Add feature to TODO.md
• Register in _pkgdown.yml