Add external data processing guide

src/data/nav/chat.ts

@@ -81,7 +81,7 @@ export default {
           link: '/docs/chat/rooms/messages',
         },
         {
-          name: 'Message storage and history',
+          name: 'Message history',
           link: '/docs/chat/rooms/history',
         },
         {
@@ -114,6 +114,28 @@ export default {
         },
       ],
     },
+    {
+      name: 'External storage and processing',
+      pages: [
+        {
+          name: 'Overview',
+          link: '/docs/chat/external-storage-and-processing',
+          index: true,
+        },
+        {
+          name: 'Data extraction',
+          link: '/docs/chat/external-storage-and-processing/data-extraction',
+        },
+        {
+          name: 'Data processing',
+          link: '/docs/chat/external-storage-and-processing/data-processing',
+        },
+        {
+          name: 'Data storage',
+          link: '/docs/chat/external-storage-and-processing/data-storage',
+        },
+      ],
+    },
     {
       name: 'React UI Kit',
       pages: [