Allow handleSubmit to accept arguments for conditional submits.

[mfrancis107]

Sometimes you may have a form with multiple submit buttons. Each may have a slightly different behavior.
For example, "Save and Continue" or "Save and Copy".

form.hanldeSubmit(true)

useForm({
  onSubmit: ({values, formApi, submitValue}) => {
     if(submitValue){
      // do x
     } else {
       // do y
     }
   }
});

Not sure about type safety. May just have to say submitValue is unknown.