Docs: a document inside every record — Add a Doc field

In the field editor, add a field and choose Doc. Every record then has a doc of its own. The grid shows how each one starts, or Write where nothing is written yet. Click that, or press Enter on the cell, and the doc opens on its own page with room to write. The record page and the side drawer show the opening of the doc with an Open button, and Start writing on a record that has nothing yet.