Please add perch_shop_category() to Paypal shop docs

I've just been stupidly trying to milk a single Paypal shop category name out of perch_shop_custom() and perch_shop_categories() without luck :(

Thought there might be some other shop specific functions in the docs only to find: https://docs.grabaperch.com/addons/shop-paypal/page-functions/standard/

Eventually found perch_shop_category() in the example files... yay!

I really should have thought of this earlier, I know but nonetheless... please could you add this function to the docs?