Add utf8 with bom (#2641)

* Change default file encoding

src/Sdk/DTWebApi/WebApi/TaskAgentSession.cs

@@ -19,7 +19,7 @@ namespace GitHub.DistributedTask.WebApi
         /// <param name="ownerName">The name of the owner for this session. This should typically be the agent machine</param>
         /// <param name="agent">The target agent for the session</param>
         public TaskAgentSession(
-            String ownerName, 
+            String ownerName,
             TaskAgentReference agent)
         {
             this.Agent = agent;