Window rounded corners are visible in borderless fullscreen mode on Windows 11

[Calinou]

OS: Windows 11
Ironwail version: 0.8.3

When playing in borderless fullscreen mode, rounded corners are visible in the bottom-left and bottom-right corners:

(The issue won't be visible on in-game screenshots and may not be visible on OS screenshot tools, so I had to take a photo of the screen.)

Windows 11 has an API to disable rounded window corners, which can be used to fix this. This code should do it:

const bool use_sharp_corners = true;
DWORD value = use_sharp_corners ? DWMWCP_DONOTROUND : DWMWCP_DEFAULT;
DwmSetWindowAttribute(wd.hWnd, DWMWA_WINDOW_CORNER_PREFERENCE, &value, sizeof(value));