Fix forward compile issues

Author: TheMeinerLP

demo/src/main/java/net/minestom/demo/PlayerInit.java

@@ -53,6 +53,7 @@
 import net.minestom.server.monitoring.TickMonitor;
 import net.minestom.server.network.packet.server.common.CustomReportDetailsPacket;
 import net.minestom.server.network.packet.server.common.ServerLinksPacket;
+import net.minestom.server.notifications.Notification;
 import net.minestom.server.potion.CustomPotionEffect;
 import net.minestom.server.potion.PotionEffect;
 import net.minestom.server.sound.SoundEvent;