Document how to require local recipes under Getting Started

Ran into this today and it took me a couple of steps to realize that I needed to add my local packages to my site's composer.json for it to manage my recipe's dependencies. Not sure how common of a use case it is, but could be helpful for those who are developing/creating recipes in a monorepo. Hope this is okay!

Great addition. Thanks for the contribution!

Automatically closed - issue fixed for 2 weeks with no activity.