implement the activity system

src/main/java/emu/grasscutter/game/activity/ActivityConfigItem.java

@@ -0,0 +1,21 @@
+package emu.grasscutter.game.activity;
+
+import lombok.AccessLevel;
+import lombok.Data;
+import lombok.experimental.FieldDefaults;
+
+import java.util.Date;
+import java.util.List;
+
+@Data
+@FieldDefaults(level = AccessLevel.PRIVATE)
+public class ActivityConfigItem {
+    int activityId;
+    int activityType;
+    int scheduleId;
+    List<Integer> meetCondList;
+    Date beginTime;
+    Date endTime;
+
+    transient ActivityHandler activityHandler;
+}