indicate that Main can now be async-ified

docs/getting-started/1-integrating.md

@@ -34,9 +34,10 @@ The following code is added to MyApp `Program.cs` to cause the application to ch
 
 ~~~cs
 using Squirrel;
+using System.Threading.Tasks;
 ~~~
 
-**`static void Main()`**
+**`static async Task Main()`**
 
 ~~~cs
 using (var mgr = new UpdateManager("C:\\Projects\\MyApp\\Releases"))