Add flag button to report spam/inappropriate content

Created by: ericmartinezr

Add flag button for spam/inappropriate content.

Currently, Admins/moderators in the channel can do something about it, but they can't be around the whole day checking the chat room. It would be nice to have a flag button which gives us the option to notify either Gitter's admins or room admins so they can do something about it. Or maybe something like 'vote for ban' (knowing the danger of misuse) where if a user reaches X votes to be banned the system will ban him automatically (and the option to the user to appeal in case of misuse).

I think it would be really nice to have something like this 👍