Allow List.Accordion to behave as a controlled component

[vieiralucas]

Motivation

This PR aims to FIX #616 and FIX #635 and CLOSE #618
It allows the List.Accordion to behave as a controlled component by passing a expanded and onPress prop.
This also enables users to start the accordion as expanded.

Test plan

I added a controlled List.Accordion to the example app and also added a snapshot test.

Thank you @jimmiehansson for starting this out in #618, I left your commits on my branch so you can take your deserved credits ❤️

[callstack-bot]

Hey @vieiralucas, thank you for your pull request 🤗. The documentation from this branch can be viewed here. Please remember to update Typescript types if you changed API.

[vieiralucas]

I tried my best to improve the docs so the user understands that he needs to pass onPress if he passes expanded.
Also I'm not sure if onPress is the best name for the callback

Thanks

[vieiralucas]

Can I propose a little refactor for this method?

const onPressIsFunction = typeof this.props.onPress === 'function';
const expandedPropIsDefined = this.props.expanded !== undefined;

if (expandedPropIsDefined) {
  if (!onPressIsFunction) {
    throw new Error(
      'The `onPress` prop must be passed when the `expanded` prop is passed to List.Accordion.'
    );
  }

  this.props.onPress();
  return;
}

if (onPressIsFunction) {
  this.props.onPress();
}

this.setState(state => ({
  expanded: !state.expanded,
}));