Give some roles the ability to send secret messages within that role in a public channel

Besides a developer server we also have a customer server where they can give suggestions and report bugs.

Today I wanted to briefly say something about a bug to other developers that I didn't really want the user to see, as it was more internal information. It would've been nice to have a command like `/hide [role] [message]` that only people with that role can see. I could've typed: `/hide @dev isn't that fixed in canary?` and then get a quick answer. Without going to DMs.