feature(widget): simple implementation of widget

Simple implementation of a part of the gadget support, very rough, hard code variables, I am very sorry for that. It can now handle part of the gadget rig. More features and better support await PRs from others. if no one else does, I'll give it a try.

src/main/java/emu/grasscutter/server/packet/send/PacketGetWidgetSlotRsp.java

@@ -0,0 +1,41 @@
+package emu.grasscutter.server.packet.send;
+
+import emu.grasscutter.game.player.Player;
+import emu.grasscutter.net.packet.BasePacket;
+import emu.grasscutter.net.packet.PacketOpcodes;
+import emu.grasscutter.net.proto.GetWidgetSlotRspOuterClass;
+import emu.grasscutter.net.proto.WidgetSlotDataOuterClass;
+import emu.grasscutter.net.proto.WidgetSlotTagOuterClass;
+
+import java.util.List;
+
+public class PacketGetWidgetSlotRsp extends BasePacket {
+
+    public PacketGetWidgetSlotRsp(Player player) {
+        super(PacketOpcodes.GetWidgetSlotRsp);
+
+        GetWidgetSlotRspOuterClass.GetWidgetSlotRsp.Builder proto =
+                GetWidgetSlotRspOuterClass.GetWidgetSlotRsp.newBuilder();
+
+        if (player.getWidgetId() == null) {
+            proto.addAllSlotList(List.of());
+        } else {
+            proto.addSlotList(
+                    WidgetSlotDataOuterClass.WidgetSlotData.newBuilder()
+                            .setIsActive(true)
+                            .setMaterialId(player.getWidgetId())
+                            .build()
+            );
+
+            proto.addSlotList(
+                    WidgetSlotDataOuterClass.WidgetSlotData.newBuilder()
+                            .setTag(WidgetSlotTagOuterClass.WidgetSlotTag.WIDGET_SLOT_ATTACH_AVATAR)
+                            .build()
+            );
+        }
+
+        GetWidgetSlotRspOuterClass.GetWidgetSlotRsp protoData = proto.build();
+
+        this.setData(protoData);
+    }
+}