SPIGOT-1806: Implement HumanEntity#getMainHand

src/main/java/org/bukkit/craftbukkit/entity/CraftHumanEntity.java

@@ -7,6 +7,7 @@ import net.minecraft.server.*;
 
 import org.bukkit.GameMode;
 import org.bukkit.Location;
+import org.bukkit.inventory.MainHand;
 import org.bukkit.Material;
 import org.bukkit.entity.HumanEntity;
 import org.bukkit.event.inventory.InventoryType;
@@ -60,6 +61,10 @@ public class CraftHumanEntity extends CraftLivingEntity implements HumanEntity {
         return enderChest;
     }
 
+    public MainHand getMainHand() {
+        return getHandle().cr() == EnumMainHand.LEFT ? MainHand.LEFT : MainHand.RIGHT; // PAIL Rename cr()->getMainHand()
+    }
+
     public ItemStack getItemInHand() {
         return getInventory().getItemInHand();
     }