Support operating system-specific features like more colors and font style

[Athari]

Windows 10 supports 256 colors now, see Orange text color in C# console application?

For *nix, it depends on the used terminal app(?). The flags are kinda standard though, so bold-italic-underline-blink flags are either supported or ignored, so should be supported by the library. The fact that "bold" often means "brigher set of forecolors" kinda sucks though.