Add confirmation for canceling comments

[DraconicNEO]

Requirements

• This is a feature request and not a bug report. Otherwise, please create a new bug report instead.
• Please check to see if this request (or a similar one) already exists.
• It's a single feature. Please don't request multiple features in one issue.

Describe the feature you'd like

I think it would be a good idea to add confirmation for canceling a comment because as it is right now it is way too easy to accidentally cancel a long comment completely trashing it, and it's also very frustrating for it to happen.
It would be good if a confirmation box popped up warning you before canceling and discarding the comment you had written. A similar warning is shown by the browser if you try to refresh the page, we should show our own warning and confirmation before a user cancels their comment or edit.