Merge pull request #4568 from deathbeam/proper-shutdown

Properly shutdown everything on window close

runelite-api/src/main/java/net/runelite/api/GameEngine.java

@@ -51,4 +51,9 @@ public interface GameEngine
 	 * @return true if on the main thread, false otherwise
 	 */
 	boolean isClientThread();
+
+	/**
+	 * Shut downs all open connections and files in client and serializes not serialized data.
+	 */
+	void shutDown();
 }