What does it fix?
This mod fixes this bug: MC-121706 via the fix suggested in that page.
Bug demonstration
This bug causes Skeletons to not look at the player when aiming, specially notable when the player is in a Y coordinate higher than the Skeleton, making them unfair to fight and unpredictable, because you don't know if the skeleton is really tracking you or not.
You can see the difference here:
Vanilla:
Skeleton Aiming Fix:
Modpack
Feel free to add it to your modpacks! You can put a link to it or not in the description, it will appear on the dependency page regardless.