Update windows example

[craigmac]

Instructions were not clear on what environment it should be run (cmd.exe, WSL, mingw, etc., etc.) and didn't work under cmd.exe. I've changed the example to use what works in cmd.exe, which I believe most people on Windows are familiar with.

[savq]

The snippet comes from #15, but it doesn't say what shell it's supposed to run on. I assumed it was cmd.exe, but then again, I know very little about Windows 🤷‍♂️