Add info that @zillowgroup/react-slider is now react-slider

[hinok]

Hey, I think it's worth to publish new version on https://www.npmjs.com/package/@zillowgroup/react-slider and updating readme and also adding specific package.json properties to inform people that package has moved from @zillowgroup/react-slider to react-slider.

[stonebk]

Good point! I'll make sure to do that, thanks!

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stonebk]

Done!