feat: Windows support

[mohammed90]

I ripped the Windows parts out into this PR because it isn't ready and clean. The Windows authentication works and authenticates against the user's password on the system. The issue is with the PTY spawn.

PTY on Windows comes in 2 flavors, both of which have their own issues.

• One approach is using an external DLL and executable from https://github.com/rprichard/winpty. This works, but the session is not jailed to the user owning the login token. It spawns the session as the user of which the ssh server is running. This is not helpful since most likely it'll be an admin or system user, which isn't safe.
• The other approach is using the new ConPTY. I had permission issues when I tried this. Windows said something about not being allowed to execute the powershell and CMD executables.