Removes some redundancy between various classes

src/main/java/net/knarcraft/minigames/arena/Arena.java

@@ -3,6 +3,7 @@ package net.knarcraft.minigames.arena;
 import org.bukkit.Location;
 import org.bukkit.block.Block;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.UUID;
 
@@ -83,4 +84,11 @@ public interface Arena {
      */
     @NotNull Location getSpawnLocation();
 
+    /**
+     * Gets this arena's exit location
+     *
+     * @return <p>This arena's exit location, or null if no such location is set.</p>
+     */
+    @Nullable Location getExitLocation();
+
 }