Villagers follow Emeralds blocks, Emerald Ore, emeralds & Deepslate Emerald Ore when held in hand. Works on the client if you're playing in singleplayer. You just need to install it on the server for it to work on there.
No support given, I'm not a dev, just a text jockey.
For those coming in the future, you need to edit villagerInitMixin.java & emerald_items.json to include the items/blocks you want them to follow