https://emojito.meme/ is really cool and almost works, except it doesn't distribute the events it creates to your relays properly so it needs a little extra help. Besides that it works with Ditto and a handful of other Nostr apps.
Discussion
I tried your link and i was able to add a little Bitcoin icon as a reaction. It's pretty useful.
The only problem is the icon doesn't work beside my username or in my profile description which is what I am looking for, maybe I can request on GitHub to amethyst to allow us to use that site emojis on our username and profile description.
Nevertheless, I'll be using it for reactions. thanks