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/Heading/H2/index.tsx

@@ -0,0 +1,32 @@
+import clsx from "clsx"
+import React from "react"
+import { Link } from "@/components"
+
+type H2Props = React.HTMLAttributes<HTMLHeadingElement> & {
+  id?: string
+  passRef?: React.RefObject<HTMLHeadingElement>
+}
+
+export const H2 = ({ className, children, passRef, ...props }: H2Props) => {
+  return (
+    <h2
+      className={clsx(
+        "h2-docs [&_code]:!h2-docs [&_code]:!font-mono mb-docs_1 mt-docs_4 text-medusa-fg-base",
+        props.id && "group/h2 scroll-m-56",
+        className
+      )}
+      {...props}
+      ref={passRef}
+    >
+      {children}
+      {props.id && (
+        <Link
+          href={`#${props.id}`}
+          className="opacity-0 group-hover/h2:opacity-100 transition-opacity ml-docs_0.5 inline-block"
+        >
+          #
+        </Link>
+      )}
+    </h2>
+  )
+}