implement shopMail giftPackage function

Co-authored-by: Kinesis <CCasusensa@users.noreply.github.com>

src/main/java/emu/grasscutter/data/common/RewardBoxItemData.java

@@ -0,0 +1,22 @@
+package emu.grasscutter.data.common;
+
+public class RewardBoxItemData {
+    private int Id;
+    private String Count;
+
+    public int getItemId() {
+        return Id;
+    }
+
+    public void setItemId(int itemId) {
+        Id = itemId;
+    }
+
+    public String getItemCount() {
+        return Count;
+    }
+
+    public void setItemCount(String itemCount) {
+        Count = itemCount;
+    }
+}