Center window for desktop app

[Zhoucheng133]

Center the window when startup.

Referenced from window_manager

[hiddify-com]

Thanks for your PR.
Would you please restore the location and size to the last location and size?
and put in center for the first time

[Zhoucheng133]

Thanks for your PR. Would you please restore the location and size to the last location and size? and put in center for the first time

I think this function should use shared_preference to store location and size when user change the size or position of the window.