Import multiple groceries as text

Request via email:

> copy/paste multiple elements into the grocery list, i.e. from Email app

Probably need these as part of this:
- editing groceries in the current list
- accept text imports via share sheet

Start by reviewing the current grocery list and the share sheet entry point described in the request, including how the Email app supplies copied text. Define how multiple pasted items are separated and edited in the current list; done means text from the share sheet can add multiple groceries and those groceries can be edited.

Written by the indexing model from the issue text.