Add foundations:elevation to storybook

[jameskoster]

Related to #66122.

What?

Adds a page detailing elevation as a foundation of the overall design language.

Why?

To help guide end users about how to use elevation when working with the WordPress components package, or when creating new UIs.

Testing Instructions

1. npm run storybook:dev
2. Observe the new Foundations / Design language / Elevation section

Missing pieces

This PR is a draft for now. I'd welcome assistance with adding:

1. Images – it's unclear if a Storybook addon is required for this, and where any images should be hosted.
2. Internal links – I tried adding the links addon to create an internal link from the tokens section to the tokens page, but couldn't get it working.

[ciampo]

This PR is a draft for now. I'd welcome assistance with adding:

1. Images – it's unclear if a Storybook addon is required for this, and where any images should be hosted.
2. Internal links – I tried adding the links addon to create an internal link from the tokens section to the tokens page, but couldn't get it working.

@mirka is this something you can help with, since you've been taking a look at other Storybook-related tasks?

[tyxla]

Let's make sure to add a link to the Elevation tokens page once it lands in #66122.

[ciampo]

Re. links, does this section of the docs help?

[mirka]

I pushed an example for adding images: ea10ad0

[jameskoster]

Thanks y'all, I added a link to the tokens section, obviously it will be broken until #66122 is merged, so let's hold off on this one until then.

[github-actions]

Flaky tests detected in 9e8f2e8.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/11403553684
📝 Reported issues:

• [Flaky Test] should close the inserter when clicking on the toggle button #48005 in /test/e2e/specs/editor/various/inserting-blocks.spec.js

[github-actions]

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Co-authored-by: jameskoster <jameskoster@git.wordpress.org>
Co-authored-by: mirka <0mirka00@git.wordpress.org>
Co-authored-by: ciampo <mciampini@git.wordpress.org>
Co-authored-by: tyxla <tyxla@git.wordpress.org>

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[ciampo]

Rebased to include the tokens page, and applied a few improvements / fixes.

Code-wise, this is LGTM 🚀

I'll leave it to @WordPress/gutenberg-design to merge it when they're happy with the contents of the page.

[jameskoster]

Added an internal link from the tokens page to the foundation page. I think this is good as an initial iteration :)

[jameskoster]

Disabled auto-merge. I noticed a couple of copy tweaks to make, and I'm going to add a graphic to better demonstrate the examples :)

[ciampo]

Cool! I'll leave the merging to you :)