Useful to be able to see who reacted

**Describe the solution you'd like**

- "View reactions" menu button
- Hover text
- Click/tap messagte to expand?

Some ideas. I don't mind the impl just need to be able to see who sent what reaction

Start by reviewing the existing message reaction UI and how reaction events are represented in the client. Compare the proposed menu, hover, and tap approaches, then define a way to reveal each reaction sender; the work is done when users can reliably see who sent every reaction on supported message layouts.

Written by the indexing model from the issue text.