Include headers in add_executable since it might be nice to have them in say Code::Blocks projects.
Include headers in add_executable since it might be nice to have them in
say Code::Blocks projects.

Signed-off-by: Harley Laue <c8a0c029c1a7cee0af4c3de9665bbb05f63c8770@gmail.com>

losinggeneration/sdl4cpp,losinggeneration/sdl4cpp