Added Window Title on Windows

[gertdreyer]

I have added functionality to get the window title on Windows. Unfortunately, I do not have a Linux or Mac machine set up to do the same for those.

I am not too up to date on the Rust best practices but L28 seems like a possible race condition to me as the window handle is retrieved again inside the self.get_position() call.

[dimusic]

Thanks!
I updated linux and macos apis to return an empty string for now, I'll try to implement it properly later.

Also the issue you brought up with repeated call to get the window handle looks like an actual bug. I'll fix it later or feel free to make another pull request.