Give access to touched state of fields when submitting

[TPReal]

Is your feature request related to a problem? Please describe.
When submitting, I sometimes only want to send fields that are actually changed, PATCH-style. Right now it's not easy to access information whether a field is modified in onSubmit.

Describe the solution you'd like
The context passed to onSubmit seems to only have setTouched and other setters, but no getters. Maybe it could have some?

Describe alternatives you've considered
The form object has the touched information on itself, but in my case the form object is wrapped inside a component which takes onSubmit as a parameter. As a result these parts are not easily accessible.

Additional context
I'm using Felte with SolidJS.