public class CapabilityHandler {
    @SubscribeEvent
    public static void onAttachCapabilities(AttachCapabilitiesEvent<Entity> event) {
        if (isArmorableMob(event.getObject())) {
            event.addCapability(new ResourceLocation(HardSteel.modid, "rearmer"), new ReArmerProvider());
        }
    }

    public static boolean isArmorableMob(Entity entity){
        if((entity instanceof ZombieEntity) || // covers Zombies, Husks, Zombie Villagers and Zombie Pigmen
                (entity instanceof SkeletonEntity) ||
                (entity instanceof StrayEntity) ||
                (entity instanceof WitherSkeletonEntity)) return true;
        return false;
    }
}