Add a `@triagebot read` command for zulip

[jackh726]

In many team meetings, there is often a doc everyone starts by reading. Usually someone manually adds the 📖 and ✅ emojis for people to click when they start and finish reading, respectively. It would be nice to just be able to do @triagebot read.

[Mark-Simulacrum]

This should mostly be a matter of replicating the existing end-topic/end-meeting support.

[apiraino]

I'll give a stab at this

@rustbot claim