There isn't an easy way to do this yet, without replacing the whole existing set, but this can be done with a new file containing the current emoji and additions.
Download and unzip the attached emoji.json file, and place it somewhere convenient on your site, eg: media/jce/emoji
Edit the file, and add the emoji you want to the bottom of the list, or replace existing emoji with your own (you can edit the list to contain just a few).
Use -
https://emojipedia.org/ - to find the emoji you want, then select and copy the icon (using CTRL + V) and the accompanying description, and then add it to the file in the same format, eg:
"❤️" : "Red Heart"
When finished, add the path to this emoji.json file in the Emoticons parameters, eg:
Ryan Demmer
Lead Developer / CEO / CTO
Just because you're not paranoid doesn't mean everybody isn't out to get you.