Add strict mode wrapper to Storybook Stories

[interactivellama]

Wrap Storybook examples in React.strictMode to aid contributors in good practices.

https://reactjs.org/docs/strict-mode.html
https://kentcdodds.com/blog/react-strict-mode

[jvitela]

Hi @interactivellama, is this different from this other issue? storybookjs/storybook#12734 (comment)