Add PlayerClientLoadedWorldEvent (#11940)

paper-api/src/main/java/io/papermc/paper/event/player/PlayerClientLoadedWorldEvent.java

@@ -0,0 +1,46 @@
+package io.papermc.paper.event.player;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.player.PlayerEvent;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Called when a player is marked as loaded.
+ * <p>
+ * This either happens when the player notifies the server after loading the world (closing the downloading terrain screen)
+ * or when the player has not done so for 60 ticks after joining the server or respawning.
+ */
+@NullMarked
+public class PlayerClientLoadedWorldEvent extends PlayerEvent {
+
+    private static final HandlerList HANDLER_LIST = new HandlerList();
+
+    private final boolean timeout;
+
+    @ApiStatus.Internal
+    public PlayerClientLoadedWorldEvent(final Player who, final boolean timeout) {
+        super(who);
+        this.timeout = timeout;
+    }
+
+    /**
+     * True if the event was triggered because the server has not been notified by the player
+     * for 60 ticks after the player joined the server or respawned.
+     *
+     * @return true if the event was triggered because of a timeout
+     */
+    public boolean isTimeout() {
+        return timeout;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLER_LIST;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLER_LIST;
+    }
+}