add references sidebar

www/apps/resources/app/references-overview/page.mdx

@@ -0,0 +1,11 @@
+import { ChildDocs } from "docs-ui"
+
+export const metadata = {
+  title: `References`,
+}
+
+# {metadata.title}
+
+This section of the documentation holds references related to the Medusa server and admin. These references are useful for your development and customizations. You can find lists of emitted events, Medusa Admin widget injection zones, built-in workflows to use in your customizations, and more.
+
+<ChildDocs hideItems={["Overview"]} defaultItemsPerRow={2} onlyTopLevel />