Storybook: Add support for publicPath.

[arunoda]

When deploying to production sites, it's better to provide a public URL. We can use webpack's publicPath field for that.

We can provide a cli argument for this. React Create App looks for the homepage field of the package.json for this.

[arunoda]

We don't use this and we don't need this.
You can deploy to any domain without any issues.

But for images, you need to do something. Check this: https://storybook.js.org/configurations/serving-static-files#absolute-versus-relative-paths

[ccutch]

Link is broken

[Hypnosphi]

@ccutch thanks, updated that