`WINDOWID` is the conventional environment variable for scripts that
want to know the X11 window ID of the terminal, so that it may call
tools like `xprop` or `xdotool`. We already know the window ID for
window protocol handling, so we might as well throw this in for
convenience.
Quoting `man man`:
> If MANPATH begins with a colon, it is appended to the default list;
Alternatively we can think about:
> if it ends with a colon, it is prepended to the default list;
To take preference over existing values, but that shouldn't be really a
problem, as there rather isn't much of another projects named `ghostty`.
Changes:
- Add WindowsPty, which uses the ConPTY API to create a pseudo console
- Pty now selects between PosixPty and WindowsPty
- Windows support in Command, including the ability to launch a process with a pseudo console
- Enable Command tests on windows
- Add some environment variable abstractions to handle the missing libc APIs on Windows
- Windows version of ReadThread
