SPIGOT-2623: Add EntityEquipment methods to get/set ItemStacks by slot.

By: blablubbabc <lukas@wirsindwir.de>

paper-api/src/main/java/org/bukkit/inventory/EntityEquipment.java

@@ -9,6 +9,23 @@ import org.jetbrains.annotations.Nullable;
  */
 public interface EntityEquipment {
 
+    /**
+     * Stores the ItemStack at the given equipment slot in the inventory.
+     *
+     * @param slot the slot to put the ItemStack
+     * @param item the ItemStack to set
+     */
+    public void setItem(@NotNull EquipmentSlot slot, @Nullable ItemStack item);
+
+    /**
+     * Gets the ItemStack at the given equipment slot in the inventory.
+     *
+     * @param slot the slot to get the ItemStack
+     * @return the ItemStack in the given slot
+     */
+    @NotNull
+    public ItemStack getItem(@NotNull EquipmentSlot slot);
+
     /**
      * Gets a copy of the item the entity is currently holding
      * in their main hand.