This removes the old compose emoji picker in its entirety, changing
the few callbacks needed to launch the reactions-style emoji picker
instead and hook it up properly.
Callbacks for reactions and composing messages are distinguished by
selecting for, respectively, the .reaction and .composition classes.
Fixes#4122.
- Expand a box full of emojis into the
compose window for users to graphically select emojis.
- Append an emoji to the end of the message when a user
clicks the emoji in the emoji box.
- Trap the escape key to always close the emoji box
before closing anything else if the box is open.
- Fixes: #147.