Enable POSIX style rendering on Windows

[vladdeSV]

On Windows, the WinApi is used to render each cell. This is highly efficient, but comes with the drawback of it being an old API. UTF-8 is not that greatly supported (AFAIK), and RGB colors cannot be used.

Newer versions of the Windows Console (PowerShell since Windows 10 at least), understands ANSI escape codes. Enabling the same rendering method on Windows would allow RGB colors.

I am not aware of any other methods to print RGB colors on Windows.

[vladdeSV]

(Horrible idea: Render every RGB color with the POSIX method, and everything else using native API calls 🤓)

[vladdeSV]

Looked at this really quickly, and a couple Dlang POSIX-only modules are not available on Windows.

I need to look at this again and once and for all figure out how everything works. (Windows Terminal only works with some WinApi functions, but can do ANSI. conhost.exe only does WinApi.)