AWS Plugin: Lambda should return list of files written to S3

plugins/tiddlywiki/aws/docs/lambda.tid

@@ -38,3 +38,9 @@ The Lambda boot code looks for an array of tiddlers to load in `event.tiddlers`,
 }
 
 ```
+
+! Return data
+
+If the Lambda function successfully executes it returns an object with the following fields:
+
+* ''lambda-result'': An array of `{bucketname,key}` pairs for each file written to S3 within the lambda function