Update hooks-README.md - shebang line in hooks on Windows.

I think letting know to users of Windows that a shebang line is expected at
the start of their non bat scripts is a good idea. I found out myself not
knowing how to make my python and node.js scripts to work as hooks until I
read cordova-lib\src\cordova\hooker.js line 77, function
extractSheBangInterpreter.

github: close #28