Make a catalogue of the DOM, then make an action to check on its freshness

[plocket]

1. Create some kind of record of every type of field and DOM-changing property
2. Write a GitHub action that, on a schedule, checks if that record still matches up with docassemble's actual DOM. Maybe checking against the examples in the docs. We may need more than those examples, though.

I've already started on 1, though I'm not sure how to best record my findings. It's not just the DOM I have, but a bunch of other notes. Each DOM unique field/property combo research should be on its own page.

We might also have to cut back on the number of combos and pick a reasonable subset. It would be a shame, but otherwise that's a lot of combinations.