docs: improvements to API reference intro sections (#9397)

- Improve intro sections of API reference to utilize divided columns
- Improve the content of the intro sections
- Add a new Workflows section to explain the workflows badge and how to use it
- Fixes to headings and add anchor for copying the link to a section
- Fixes responsiveness of intro sections on mobile devices
- Other: fix loading not showing when a sidebar category is opened.

Closes DOCS-932, DOCS-934, DOCS-937

Preview: https://api-reference-v2-git-docs-api-ref-intro-fixes-medusajs.vercel.app/v2/api/store

www/packages/docs-ui/src/components/index.ts

@@ -24,6 +24,7 @@ export * from "./ExpandableNotice"
 export * from "./FeatureFlagNotice"
 export * from "./Feedback"
 export * from "./Feedback/Solutions"
+export * from "./Heading"
 export * from "./HooksLoader"
 export * from "./Icons"
 export * from "./InlineIcon"