docs: fixes and preparations for workflows reference (#8579)

- Fix the merger configuration that adds the correct slug / sidebar labels
- Add an overview page for the workflows reference.
- Fixes to components and build scripts

www/apps/resources/app/medusa-workflows-reference/page.mdx

@@ -0,0 +1,13 @@
+import { ChildDocs } from "docs-ui"
+
+export const metadata = {
+  title: `Medusa Workflows Reference`,
+}
+
+# {metadata.title}
+
+This section of the documentation provides a reference to the workflows created by Medusa. These workflows are used in the Store and Admin API routes.
+
+You can use these workflows in your customizations as well. They're available in the `@medusajs/core-flows` package.
+
+<ChildDocs childLevel={2} />