docs: Add attachment_urls to create_conversation_request in descriptions/0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: markdennis22

descriptions/0/api.intercom.io.yaml

@@ -19283,6 +19283,14 @@ components:
           type: string
           description: The content of the message. HTML is not supported.
           example: Hello
+        attachment_urls:
+          type: array
+          description: A list of image URLs that will be added as attachments. You
+            can include up to 10 URLs.
+          items:
+            type: string
+            format: uri
+          maxItems: 10
         created_at:
           type: integer
           format: date-time