Update README with a PowerShell loop example

[michaelsanford]

First, I love this tool. Thanks for creating it.

I recently had to []byte-fiy a folder of hundred of icons, in Windows, and accomplished it fairly easily with this quasi-oneliner.

Ignoring the looping, it also provides a PowerShell example (many users are on Windows) for the unititiated.

No hard feelings if you think it's too specific, or simply don't want it. 😄