Merge XP orbs

This is my first datapack, and was done in a couple minutes. (mostly debugging…)

It combines two orbs about every second, I tried a Dispenser full of XP Bottles with a fast clock into an enclosed space and the entity ammount didn't go above 5, ending with just one (1) orb when it was finished.

Considering this is the only thing that it does, it shouldn't disturb so much in compatibility, but make sure you don't use multiple mods/datapacks that do the same thing as per usual advice.