Emoji reactions

Requires develop backend that supports latest emoji reaction format.

This MR does:

• add new reactions with unicode emoji
• use search to filter through the emoji or pick one of the "common" ones
• click on existing reactions to add your own or remove it

This MR doesn't:

• have notifications for reactions
• update emoji reactions in real time

This MR should still:

• limit the amount of reactions shown per status

src/components/conversation/conversation.js

@@ -150,6 +150,7 @@ const conversation = {
       if (!id) return
       this.highlight = id
       this.$store.dispatch('fetchFavsAndRepeats', id)
+      this.$store.dispatch('fetchEmojiReactionsBy', id)
     },
     getHighlight () {
       return this.isExpanded ? this.highlight : null