adds `get_comment_annotation_ids`, `get_comment_annotation`, `post_comment_annotation`

[erickmartins]

Description

Three functions that replicate functionality that already exists for MapAnnotations, but for CommentAnnotations.

Checklist

Tests, flake8, mypy type hint checks passing.

For reviewers

• Check that the PR title is short, concise, and will make sense 1 year later.
• Check that new functions are imported in corresponding __init__.py.