[UX] Enable use of core HTML5 Date widget for date field

[yorkshire-pudding]

It would improve things, particularly for mobile users if we could enable the HTML5 Date widget for the date component.

[herbdool]

I took a look. A bit of work. Not just adding an alternative widget but changing the settings, validation and submission too. All of which are assuming there are select fields. I may wait until someone needs it for a project and provides a PR, or a client needs it.