impl pre shutdown saving

src/main/java/cc/fascinated/bat/event/EventListener.java

@@ -104,4 +104,10 @@ public interface EventListener {
      */
     default void onGuildMemberUpdateNickname(@NonNull BatGuild guild, @NonNull BatUser user, String oldName, String newName, @NonNull GuildMemberUpdateNicknameEvent event) {
     }
+
+    /**
+     * Called when Spring is shutting down
+     */
+    default void onSpringShutdown() {
+    }
 }