docs: added malchimp integration guide (#12807)

* docs: added malchimp integration guide

* add edit date

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

@@ -120,6 +120,13 @@ While tutorials show you a specific use case, they also help you understand how
         path: "/integrations/guides/magento",
         description: "Learn how to migrate data from Magento to Medusa.",
       },
+      {
+        type: "ref",
+        title: "Newsletter with Mailchimp",
+        path: "/integrations/guides/mailchimp",
+        description:
+          "Learn how to integrate Mailchimp with Medusa to manage and automate newsletters.",
+      },
       {
         type: "link",
         title: "Phone Authentication",