[Windows] WinPTY support for Windows < 1809

[cocoa-xu]

Windows support is possible by utilizing the Windows conpty API on Windows 1809+ and the winpty library in older version.

As mentioned in microsoft/node-pty, Windows conpty API is only available after Windows 1809 (including), so for previous versions, we have to use WinPTY.

I'll add this support later, maybe in a month. It was traumatising when developing something on Windows.

[cocoa-xu]

It has almost been a year since I wrote down this issue, and now I think it's not necessary to implement this feature as Windows 1809 has already passed its eol date.

However, it's likely that there are still some people who are using these versions of Windows. Therefore, I decided to do this if there're people requesting this feature under this issue.