Is your feature request related to a problem? Please describe.
I am currently unit testing my TUI application using bubbletea. I found it unintuitive that when setting a field's value, you cannot immediately retrieve the results after creating a form.

func TestFilledForm(t *testing.T) {
	event := sampleEvent()
	f := filledEventForm(EventWrapper{&event})

	// huh forms do not set the results until processing nextFieldMsg through all fields
	for i := 0; i < 50; i++ {
		f.Update(f.NextField())
	}

	if f.GetString("summary") != event.Summary {
		t.Errorf("Summary: %v != %v", f.Get("summary"), event.Summary)
	}

	if f.GetString("description") != event.Description {
		t.Errorf("Description: %v != %v", f.Get("description"), event.Summary)
	}

	if f.GetString("start") != event.Start.DateTime {
		t.Errorf("Start: %v != %v", f.Get("start"), event.Start.DateTime)
	}

	if f.GetString("end") != event.End.DateTime {
		t.Errorf("End: %v != %v", f.Get("end"), event.End.DateTime)
	}

	if f.GetString("location") != event.Location {
		t.Errorf("Location: %v != %v", f.GetString("location"), event.Location)
	}
}

Describe the solution you'd like
A clear and concise description of what you want to happen.

Within NewForm(), I would like to set the results to any existing values for fields within it.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

I can always call NextField() in the Form setup for my unit tests, but I figure this behavior might confuse some users in the future.

Additional context

I just want to make sure if there is a specific choice for forms to work this way. If it is not intended, I can take a stab at it. I'm learning Go right now, and I think it would be a good opportunity.