Add ability to run from powershell or CMD prompt on Windows

[djha-skin]

Right now, I can't just run qlot install on Windows from a CMD prompt. In order to do so, I have to have this script, named rsc.bat, on my PATH:

@echo off
ros -Q -L sbcl-bin -- C:\Users\bhw\.roswell\lisp\quicklisp\bin\%*

And run rsc qlot install instead.

This PR fixes this. By having a .bat file in the roswell directory, it gets installed into roswell's bin/ folder, which is on the windows PATH. It finds itself in the file system, and runs the roswell script that is next to it within the same directory.

By adding this file, I can now just ros install fukamachi/qlot on Windows, followed by qlot install in my project directory, and it works.

[fukamachi]

Thank you so much!