[Docs] EuiProvider custom breakpoints example no longer works

[cee-chen]

Problem

https://eui.elastic.co/#/theming/breakpoints/values#custom-values

Broken EuiProvider example:

https://github.com/elastic/eui/blob/5c4031565d1f0fef7e08e2377ea5b29bf8963b54/packages/eui/src-docs/src/views/theme/breakpoints/breakpoints.tsx#L54

The PR that broke this was https://github.com/elastic/eui/pull/6949 - we now return early for nested EuiProviders, meaning there can only be one top-level provider on each page, meaning the example is now broken 😅

Solution

• One quick fix could be creating a Storybook with custom breakpoints and then embedding it as an iframe
• Alternatively, we could simply wait until EUI+ where everything will be on Storybook embeds at that point in any case

[JasonStoltz]

This should be fixed when we roll out our new documentation site, which is slated for the end of this quarter.