ACCESSIBILITY: readonly fields should be <input readonly >

[tractorcow]

At the moment we use <FormControl.Static /> in react which doesn't produce proper input tags. I suggest that we should probably stick with literal inputs for all input-type fields, and flag these with either disabled or readonly html properties.

This distinguishes readonly inputs from literals (provided by LiteralField).

[dhensby]

is this going to be actioned?

[tractorcow]

At some point yeah. When I get more time. :)