Update README.md

Author: cdavernas

README.md

@@ -23,6 +23,10 @@ With the SDK, you can:
 dotnet nuget add package ServerlessWorkflow.Sdk
 ```
 
+```csharp
+services.AddServerlessWorkflow();
+```
+
 ### How to use
 
 #### Building workflows programatically
@@ -78,3 +82,10 @@ using(Stream stream = File.OpenRead("myWorkflow.json"))
       }
   }
 ```
+
+#### Validating workflows
+
+```csharp
+var validator = serviceProvider.GetRequiredService<IValidator<WorkflowDefinition>>();
+var validationResult = validator.Validate(myWorkflow);
+```