feat: add elicitation/create to spec

Author: Avcharov

specification/draft/apps.mdx

@@ -516,6 +516,10 @@ UI iframes can use the following subset of standard MCP protocol messages:
 
 - `resources/read` - Read resource content
 
+**Elicitation:**
+
+- `elicitation/create` - Request structured user input via the host
+
 **Notifications:**
 
 - `notifications/message` - Log messages to host