Hi Di,
it won't automatically compile it for you as it would in your theme folder. You will have to do that yourself. I tend to use gulp in my plugins so it doesn't get mixed up with Moodle's use of grunt. You can find an example of how I used it in one of my plugins: https://github.com/sharpchi/moodle-local_accessibilitytool/blob/master/gulpfile.js
You'll need to have nodejs installed to use it.