Create Storybook guideline and add addon-designs to embed Figma (#27310)

* Add foundations and migrations docs

* Add storybook/addon-designs version 8.2.1

* Test Figma link

* Refactor Modal stories

* Create figmaDesignUrl

* Create foundations

* Create feature flags docs

* Create Storybook builds docs

* Add storybook/addon-designs version 8.2.1

* Test Figma link

* Add an example of Story with split-tests within the Storybook guidelines (#27260)

* Add FormatCurrency demo in feature-flags.mdx

* Add syntax highlight to code samples

* Update stories with figmaDesignUrl

* Figma access token

* Use OLButton

* Hide control for children and footer

* Add primitive colors

* Use useSplitTest instead

* Update cloud builds docs with `storybook-push-trigger`

* Make Foundations the default story

---------

Co-authored-by: Antoine Clausse <antoine.clausse@overleaf.com>
GitOrigin-RevId: 0729759803f190d89cf543d087eea86265b725f1

services/web/package.json

@@ -218,6 +218,7 @@
     "@replit/codemirror-vim": "overleaf/codemirror-vim#1bef138382d948018f3f9b8a4d7a70ab61774e4b",
     "@sentry/browser": "7.46.0",
     "@storybook/addon-a11y": "^8.6.12",
+    "@storybook/addon-designs": "^8.2.1",
     "@storybook/addon-essentials": "^8.6.12",
     "@storybook/addon-interactions": "^8.6.12",
     "@storybook/addon-links": "^8.6.12",