docs: integrate payload guide (#13162)

* docs: integrate payload guide

* remove todo

* fix vale errors

* change items per row in integrations page

* updates to guide

www/apps/resources/sidebars/how-to-tutorials.mjs

@@ -121,6 +121,13 @@ While tutorials show you a specific use case, they also help you understand how
         description:
           "Learn how to generate invoices for orders in your Medusa store.",
       },
+      {
+        type: "ref",
+        title: "Integrate Payload CMS",
+        path: "/integrations/guides/payload",
+        description:
+          "Learn how to integrate Payload CMS with Medusa to manage your product content.",
+      },
       {
         type: "link",
         title: "Loyalty Points System",