Emoji reactions on comments

[ndubinkin]

Hi everyone! Thank you for the great product.

It would be awesome to have the ability to add reactions to comments. At least the basic ones (like/dislike), but ideally any emojis. This is already a familiar feature for users, and sometimes it's much more convenient than writing a reply. A reply triggers notifications for everyone subscribed to the card, whereas reactions could be silent (without triggering notifications).

However, it's important to display who exactly left the reaction (e.g., via a tooltip on hover or in some other way).

[ilyachase]

Probably duplicates #122