Add Step Functions as a Supported Service (#33149)

Author: ryanstrat

content/en/serverless/aws_lambda/distributed_tracing.md

@@ -61,6 +61,7 @@ The Datadog Lambda Library and tracing libraries for Python and Node.js support:
   - EventBridge
   - DynamoDB
   - S3
+  - Step Functions
 - Tracing dozens of additional out-of-the-box [Python][3] and [Node.js][4] libraries.
 
 For Python and Node.js serverless applications, Datadog recommends you [install Datadog's tracing libraries][5].
@@ -407,4 +408,4 @@ If you are already tracing your serverless application with X-Ray and want to co
 [31]: https://github.com/DataDog/dd-trace-py/
 [32]: https://github.com/DataDog/dd-trace-js/
 [33]: https://github.com/DataDog/datadog-lambda-python
-[34]: https://github.com/DataDog/datadog-lambda-js
+[34]: https://github.com/DataDog/datadog-lambda-js