Highlight/signal a question

Perusall and other tools have ways for students to signal that their annotation is a question, making it easier for other students and the instructor to help answer the question.

Federal guidelines around "regular and substantive interactions" specifically call out instructors answering student questions in real-time as a way to fulfill the RSI requirement:

> Providing information or responding to questions about the content of a course or competency;

Currently, students could use a question tag to call out a question. We could make this easier by a button signaling an annotation is a question, perhaps coloring those annotations distinctly, and enabling filtering/sorting by question.