[ChoiceList] Disable all choices at once

[jtrollia]

WHY are these changes introduced?

It can be tedious to pass down a disable prop to each choice of a <ChoiceList />, especially when the component is wrapped, or when the list of choices is long.

Mentioned in #114.

WHAT is this pull request doing?

📹 https://www.youtube.com/watch?v=r6gPRukvCbQ&feature=youtu.be

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

Copy-paste this code in playground/Playground.tsx:

import * as React from 'react';
import {Page} from '../src';
import {ChoiceList, Button} from '../src';

interface State {
  choice: string;
  massDisable: boolean;
}

export default class Playground extends React.Component<{}, State> {
  state: State = {
    choice: 'enabled',
    massDisable: false,
  };

  render() {
    const {choice, massDisable} = this.state;
    return (
      <Page title="Playground">
        <ChoiceList
          choices={[
            {
              value: 'disabled',
              label: 'Disabled',
            },
            {
              value: 'enabled',
              label: 'Enabled',
            },
            {
              value: 'pepsi',
              label: 'Pepsi',
              disabled: true,
            },
          ]}
          title="Some funky ChoiceList"
          selected={[choice]}
          onChange={(newVal) => {
            this.setState({choice: newVal[0]});
          }}
          disabled={massDisable}
        />
        <br />
        <Button onClick={() => this.setState({massDisable: !massDisable})}>
          {massDisable ? 'Enable' : 'Disable'} all choices
        </Button>
      </Page>
    );
  }
}

🎩 checklist

• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility
• Updated the component's README.md with documentation changes
• Tophatted documentation changes in the style guide

[ghost]

👋 Thanks for opening your first pull request. A contributor should give feedback soon. If you haven’t already, please check out the contributing guidelines. You can also join #polaris on the Shopify Partners Slack.

[chloerice]

Changes and 🎩 look solid 🏅 Thanks for contributing Jean-Loup! Just add the following entry to the UNRELEASED.md under Enhancements and you're good 🚢

Added support for disabling all choices in `ChoiceList` ((1758)[https://github.com/Shopify/polaris-react/pull/1758])

[ghost]

🎉 Thanks for your contribution to Polaris React!