Update PlayerInventoryOverflowEvent (#304)

* Add configurable option in config for PlayerInventoryOverflowEvent and able to define the class name of listener
* Update checking method for overflow items handling logic, only fire event when actual listener is listening to it.

leaf-server/src/main/java/org/dreeam/leaf/config/modules/gameplay/ConfigurableInventoryOverflowEvent.java

@@ -0,0 +1,32 @@
+package org.dreeam.leaf.config.modules.gameplay;
+
+import org.dreeam.leaf.config.ConfigModules;
+import org.dreeam.leaf.config.EnumConfigCategory;
+
+public class ConfigurableInventoryOverflowEvent extends ConfigModules {
+
+    public String getBasePath() {
+        return EnumConfigCategory.GAMEPLAY.getBaseKeyName() + ".inventory-overflow-event";
+    }
+
+    public static boolean enabled = false;
+    public static String listenerClass = "com.example.package.PlayerInventoryOverflowEvent" ;
+
+    @Override
+    public void onLoaded() {
+        enabled = config.getBoolean(getBasePath() + ".enabled", enabled, config.pickStringRegionBased("""
+                The event called when used plugin to Inventory#addItem
+                into player's inventory, and the inventory is full.
+                This is not recommended to use, please re-design to use the
+                returned map of Inventory#addItem method as soon as possible!""",
+            """
+                此事件将在插件使用 Inventory#addItem 方法
+                添加物品到玩家背包, 但是背包已满时调用.
+                不建议使用此事件，请尽快迁移至使用 Inventory#addItem 方法
+                返回的 map"""));
+        listenerClass = config.getString(getBasePath() + ".listener-class", listenerClass, config.pickStringRegionBased("""
+                The full class name of the listener which listens to this inventory overflow event.""",
+            """
+                监听此物品栏物品溢出事件的完整类名."""));
+    }
+}