Create/Update assets for version 1.21.3

assets/minecraft/textures/entity/horse/_list.json

@@ -0,0 +1 @@
+{"directories":[],"files":["donkey.png","horse_black.png","horse_brown.png","horse_chestnut.png","horse_creamy.png","horse_darkbrown.png","horse_gray.png","horse_markings_blackdots.png","horse_markings_white.png","horse_markings_whitedots.png","horse_markings_whitefield.png","horse_skeleton.png","horse_white.png","horse_zombie.png","mule.png"]}