Submit option, only dirty values

[NielsJorck]

Is your feature request related to a problem? Please describe.
A bit of niche feature, but if we are creating a patch-merge request it should only include the values that have changed values, eg. dirty fields.
However currently we have to check each field manually and see if it is dirty or not, which is kind of a pain.

Describe the solution you'd like
If it is possible to include an options object to the handleSubmit, that could indicate which fields to target, eg. dirty fields, and only return those, that would solve this issue.

Describe alternatives you've considered
Currently it has to be handled outside of the framework, which doesn't work very well.