implement simple drop system

src/main/java/emu/grasscutter/game/drop/DropData.java

@@ -0,0 +1,57 @@
+package emu.grasscutter.game.drop;
+
+public class DropData {
+    private int minWeight;
+    private int maxWeight;
+    private int itemId;
+    private int minCount;
+    private int maxCount;
+    private boolean share = false;
+
+    public int getItemId() {
+        return itemId;
+    }
+
+    public void setItemId(int itemId) {
+        this.itemId = itemId;
+    }
+
+    public int getMinCount() {
+        return minCount;
+    }
+
+
+    public int getMaxCount() {
+        return maxCount;
+    }
+
+
+    public int getMinWeight() {
+        return minWeight;
+    }
+
+    public int getMaxWeight() {
+        return maxWeight;
+    }
+
+
+    public boolean isShare() {
+        return share;
+    }
+
+    public void setIsShare(boolean share) {
+        this.share = share;
+    }
+
+    public boolean isGive() {
+        return give;
+    }
+
+    private boolean give = false;
+
+    public boolean isExp() {
+        return exp;
+    }
+
+    private boolean exp = false;
+}