Fix equipment slot and group API

Adds the following:
- Add missing 'body' slot group
- Expose LivingEntity#canUseSlot

Co-authored-by: SoSeDiK <mrsosedik@gmail.com>

paper-api/src/main/java/org/bukkit/entity/LivingEntity.java

@@ -1457,4 +1457,15 @@ public interface LivingEntity extends Attributable, Damageable, ProjectileSource
      */
     void setBodyYaw(float bodyYaw);
     // Paper end - body yaw API
+
+    // Paper start - Expose canUseSlot
+    /**
+     * Checks whether this entity can use the equipment slot.
+     * <br>For example, not all entities may have {@link org.bukkit.inventory.EquipmentSlot#BODY}.
+     *
+     * @param slot equipment slot
+     * @return whether this entity can use the equipment slot
+     */
+    boolean canUseEquipmentSlot(org.bukkit.inventory.@NotNull EquipmentSlot slot);
+    // Paper end - Expose canUseSlot
 }