Add emoji on note

[bitionaire]

As I user I want to add an emoji reaction to a note (e.g. if I love it or if I totally disagree)

[SelinaBuff]

Regarding to the reactions on the note, we got 2 different ideas:

1. As soon as you hover over a note, a flap unfolds downwards (see image 1).
2. Like on Github, a click opens an external emoji field (see image 2).

General things to note:

• We ultimately decide which emojis to offer (maybe give a limited choice in the first step).
• If a user has a long name we will probably have to provide a maximum of punctuation and shorten the name if necessary if they reach their maximum info (e.g. during the voting session).

[Schwehn42]

Implementation: See #2964