https://cawolfkreo.github.io/Cease-and-Desist-History-Big-N/
Example repo where it's extensively used @cawolfkreo

Small thing, the full link to the repo is this one: https://github.com/cawolfkreo/Cease-and-Desist-History-Big-N

Also, after doing some research there are packages for JS/TypeScript that could give some help implementing this, like this one.

I should also say you can fetch the image for the emoji directly from github. I don't know if it's the best way but since you do need an internet connection to fetch github data, it could also work. This means you can grab the name of the emoji between the :s and then put it on the respective url, like so:

@cawolfkreo you seem to be volunteering for this lol
I think it's a regex that finds ":godmode:" and replaces with the image

Maybe not all but a few.
Here's the source:https://github.com/rhysd/node-github-emoji/blob/master/src/emoji.json

https://docs.github.com/en/rest/emojis#get-emojis