Add IslandLevelListener.

This class listens for level calculation, and will update "unlocked" biomes for the player.

src/main/java/world/bentobox/biomes/BiomesAddon.java

@@ -17,6 +17,7 @@
 import world.bentobox.biomes.handlers.BiomeListRequestHandler;
 import world.bentobox.biomes.handlers.ChangeBiomeRequestHandler;
 import world.bentobox.biomes.listeners.ChangeOwnerListener;
+import world.bentobox.biomes.listeners.IslandLevelListener;
 import world.bentobox.biomes.listeners.JoinLeaveListener;
 import world.bentobox.biomes.managers.BiomesAddonManager;
 import world.bentobox.biomes.managers.BiomesImportManager;
@@ -91,6 +92,7 @@ private void setupAddon()
 		// Register the reset listener
         this.registerListener(new ChangeOwnerListener(this));
         this.registerListener(new JoinLeaveListener(this));
+        this.registerListener(new IslandLevelListener(this));
 
         // Register Flags
         this.registerFlag(BIOMES_WORLD_PROTECTION);

src/main/java/world/bentobox/biomes/listeners/IslandLevelListener.java

@@ -0,0 +1,59 @@
+//
+// Created by BONNe
+// Copyright - 2022
+//
+
+
+package world.bentobox.biomes.listeners;
+
+
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+
+import world.bentobox.bentobox.api.user.User;
+import world.bentobox.biomes.BiomesAddon;
+import world.bentobox.level.events.IslandLevelCalculatedEvent;
+
+
+/**
+ * The type Level listener.
+ */
+public class IslandLevelListener implements Listener
+{
+    /**
+     * Instantiates a new Level listener.
+     *
+     * @param addon the addon
+     */
+    public IslandLevelListener(BiomesAddon addon)
+    {
+        this.addon = addon;
+    }
+
+
+    /**
+     * On level up.
+     *
+     * @param event the event
+     */
+    @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
+    public void onLevelCalculated(IslandLevelCalculatedEvent event)
+    {
+        // Process event in Addon Manager.
+        this.addon.getAddonManager().checkBiomesUnlockStatus(
+            event.getIsland(),
+            User.getInstance(event.getTargetPlayer()),
+            event.getLevel());
+    }
+
+
+// ---------------------------------------------------------------------
+// Section: Variables
+// ---------------------------------------------------------------------
+
+    /**
+     * Instance of addon for event.
+     */
+    private final BiomesAddon addon;
+}