Mojang added a new behavior to villagers which is sleeping. But when villagers sleep, their eyes don't close, unlike foxes. So this resource pack makes villager's eyes close when they sleep!
This is what villagers look like when they sleep:
It makes it more realistic and not creepy when villagers sleep now because they close their eyes!
There's also a bonus feature on this resource pack where persona skins (The character creator skins) also close their eyes when they sleep!