addon-docs: Allow setting `argTypes` for `subcomponents`

Is your feature request related to a problem? Please describe I have a situation where I want to use subcomponents but I need to be able to customize some of the values displayed in the generated table. As far as I can tell, I can only apply argTypes customization to the main component, not the subcomponent.

Describe the solution you’d like A method of setting argTypes for subcomponents. I’m not sure what the best config structure would be for this, and am open to suggestions.

Describe alternatives you’ve considered N/A

Are you able to assist to bring the feature to reality? Yes, with pointers on where the relevant code is.

Additional context N/A

[AmirTugi]

How about

export default {
  title: 'Components/Calendar',
  component: Calendar,
  subcomponents: { 
    CalendarLegend: {
      component: CalendarLegend,
      argTypes: {
        label: { control: 'input' },
      },
    },
  },
  argTypes: {
    onSelect: { action: 'selected' },
  }
};

And in case we don’t want to add manual argTypes it will be left as in today -

export default {
  title: 'Components/Calendar',
  component: Calendar,
  subcomponents: { CalendarLegend },
  argTypes: {
    onSelect: { action: 'selected' },
  }
};

[Fernker]

Anyone know of a workaround for this? I find it incredible that argTables is considered a first-class citizen but there’s no support for it on subcomponents.