Player body parts as item models with their skin

I wanted to add emotes to minecraft using animated java.
But I didn't know how to make what the title says.
I found a datapack that does this but it was for 1.19 and it was from 3 years ago.
I want to know how it works and if there is a better way to do this.
Here is the resource pack: https://www.planetminecraft.com/data-pack/emotes-in-vanilla-java/