Allow Modal to be DOM snapshot tested

[interactivellama]

With React Modal 3.71, you can mock ReactDOM.createPortal which DSR Modal uses

reactjs/react-modal@fc53400#diff-bc2c6ca31effc945eed3e8b6a02d0413R14

Here is an example of how to use Jest DOM snapshots with createPortal. https://gist.github.com/505aaron/d5efc2ecc622306cbcc6d3e9c1d7ee9f

[interactivellama]

This should make the path clear to add the following components to DOM snapshots:

export AppLauncher from '../components/app-launcher/__docs__/storybook-stories';
export GlobalNavigationBar from '../components/global-navigation-bar/__docs__/storybook-stories';
export DatePicker from '../components/date-picker/__docs__/storybook-stories';
export Modal from '../components/modal/__docs__/storybook-stories';
export Panel from '../components/panel/__docs__/storybook-stories';
export TimePicker from '../components/time-picker/__docs__/storybook-stories';