<bmx-form>
A form drawn from JSON.
A form in three steps, drawn from JSON. The address shows only for delivery, each line works out its amount, the
totals follow, and postage is free from £50. Leave a field to see its check; send the form to see the summary of
problems. Answers are kept as a draft in this browser.
Every property, event and method: https://docs.binarymission.co.uk/webcomponents/bmx/bmx-form.html