A simple example resource pack to demonstrate resource pack overlays, which are added in Minecraft 1.20.2 (Changelog)
This example only changes the pumpkin blur, you get with an equipped carved pumpkin. As configured in pack.mcmeta you'll get another overlay containing a different pumpkinblur UI if the pack is loaded with pack version 18 (1.20.2).
You can download a resource pack zip here.