fix(doc): Fix markdown for API design doc

sdk/iot/Azure.Iot.Hub.Service/src/API Design.md

@@ -10,27 +10,31 @@ This document outlines the APIs for the Azure Iot Hub Service SDK
 
 <details><summary><b>Configurations</b></summary>
 APIs for managing configurations for devices and modules
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Statistics</b></summary>
 APIs for getting statistics about devices and modules, as well as service statistics
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Registry</b></summary>
 APIs for managing device and module identities
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Jobs</b></summary>
 APIs for using IotHub jobs
+
 ```csharp
 
 ```
@@ -46,41 +50,47 @@ APIs for using IotHub jobs
 
 <details><summary><b>Twin</b></summary>
 Device and module twin operations
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Methods</b></summary>
 Device and module direct methods
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Cloud to Device Messaging</b></summary>
-No sign of this in the swagger    
+No sign of this in the swagger
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Feedback Message</b></summary>
 APIs for getting feedback messages
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>File Upload Notifications</b></summary>
 No sign of this in the swagger
+
 ```csharp
 
 ```
 </details>
 
 <details><summary><b>Query</b></summary>
 APIs for querying on device or module identities
+
 ```csharp
 
 ```