Template for Elastic products

[miukimiu]

This PR updates the template to make it easier to create prototypes for our Elastic products. The old template in use was more similar to our EUI docs site and the new one is more similar to what Kibana is nowadays.

Preview

Before: https://next-eui-starter.vercel.app/

After: https://next-eui-starter-git-elastic-products-miukimiu.vercel.app/

More changes

There are two templates to make it easier to get started:

• Kibana template: https://next-eui-starter-git-elastic-products-miukimiu.vercel.app/kibana
• Docs template: https://next-eui-starter-git-elastic-products-miukimiu.vercel.app/docs

Emotion styles

• Emotion styles live in their own files like *.styles.ts.
• The styles for pages live inside the styles folder.

To do

• [x] Add more pages with different templates
• [x] Move styles to their own files *.styles.ts to follow EUI emotion pattern

[chandlerprall]

@miukimiu I've pushed up a small refactor to theming, switching and reloading appears to be working for me now.

[miukimiu]

Thanks, @chandlerprall. I tested it and it works well! 😄

[miukimiu]

Thanks, @thompsongl, @boriskirov, and @chandlerprall for all the help. 🙌🏽 I'm merging the PR.

@boriskirov you're welcome to improve the starter with smaller PRs.