LibMain: Update header includes

Author: https://github.com/ldm5180
Commit: 4e6898c5cc
Pull-request: https://github.com/SerenityOS/serenity/pull/12527
Reviewed-by: https://github.com/kleinesfilmroellchen ✅

Userland/Libraries/LibMain/Main.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -7,6 +8,8 @@
 #pragma once
 
 #include <AK/Error.h>
+#include <AK/Span.h>
+#include <AK/StringView.h>
 
 namespace Main {