docs: add link to the Slack tutorial in the integrations page (#12721)

www/apps/resources/app/integrations/page.mdx

@@ -176,6 +176,14 @@ A Notification Module Provider sends messages to users and customers in your Med
         children: "Tutorial"
       }
     },
+    {
+      href: "/integrations/guides/slack",
+      title: "Slack",
+      badge: {
+        variant: "blue",
+        children: "Tutorial"
+      }
+    },
     {
       href: "/how-to-tutorials/tutorials/phone-auth#step-3-integrate-twilio-sms",
       title: "Twilio SMS",
@@ -226,4 +234,4 @@ Integrate a search engine to index and search products or other types of data in
     }
   ]}
   className="mb-1"
-/>
+/>