SnapLayout Support

[ghost1372]

Hi @SuGar0218
I came across this project by chance. I really like your work. To support Snap Layout, you can do what I previously did in WPF — it’s not difficult.

https://github.com/ghost1372/HandyControls/blob/develop/src/Shared/HandyControl_Shared/HandyControls/Controls/Window!.cs

https://github.com/ghost1372/HandyControls/blob/ba3d05c786c7f8a0b057bfcc9726a3148b316267/src/Shared/HandyControl_Shared/Controls/Window/Window.cs#L365

[SuGar0218]

Thank you for your liking~

Currently I had supported SnapLayout by InputNonClientPointerSource but I forgot to update readme after I pushed this commit.

Supporting SnapLayout in WinUI 3 is different from WPF. A WPF window has only one HWND while a WinUI 3 window has multiple HWND. I have previously tried to handle window message, but SnapLayout only appears when the mouse hover the edge area. When I tried to support SnapLayout in WPF, the similar situation appears when the WindowChrome.GlassFrameThickness.Top is not 0, SnapLayout only appears when the mouse hover on the intersecting area of WindowChrome.GlassFrameThickness.Top and WM_NCHITTEST.