Update README with event source documentation

Author: GarrettBeatty

Libraries/src/Amazon.Lambda.Annotations/README.md

@@ -20,6 +20,7 @@ Topics:
   - [Amazon S3 example](#amazon-s3-example)
   - [SQS Event Example](#sqs-event-example)
   - [Application Load Balancer (ALB) Example](#application-load-balancer-alb-example)
+  - [DynamoDB Event Example](#dynamodb-event-example)
   - [Custom Lambda Authorizer Example](#custom-lambda-authorizer-example)
     - [HTTP API Authorizer](#http-api-authorizer)
     - [REST API Authorizer](#rest-api-authorizer)
@@ -1073,6 +1074,27 @@ The `ALBApi` attribute requires an existing ALB listener. Here is a minimal exam
 
 Then your Lambda function references `@MyListener` in the `ALBApi` attribute.
 
+## DynamoDB Event Example
+This example shows how to use the `DynamoDBEvent` attribute to set up event source mapping between a DynamoDB stream and a Lambda function.
+
+The `DynamoDBEvent` attribute contains the following properties:
+* **Stream** (Required) - The DynamoDB stream ARN or a reference to a DynamoDB table resource prefixed with "@". When using a resource reference, the source generator uses `Fn::GetAtt` to get the `StreamArn`.
+* **ResourceName** (Optional) - The CloudFormation resource name for the event source mapping.
+* **StartingPosition** (Optional) - The position in the stream to start reading. Valid values: `TRIM_HORIZON`, `LATEST`. Default is `LATEST`.
+* **BatchSize** (Optional) - The maximum number of records per batch. Must be between 1 and 10000. Default is 100.
+* **MaximumBatchingWindowInSeconds** (Optional) - Maximum time to gather records before invoking. Must be between 0 and 300.
+* **Enabled** (Optional) - If false, the event source mapping is disabled. Default is true.
+* **Filters** (Optional) - Semicolon-separated filter patterns for event filtering.
+
+```csharp
+[LambdaFunction(ResourceName = "DynamoDBStreamHandler", Policies = "AWSLambdaDynamoDBExecutionRole", PackageType = LambdaPackageType.Image)]
+[DynamoDBEvent("@TestTable", ResourceName = "TestTableStream", BatchSize = 100, StartingPosition = "TRIM_HORIZON")]
+public void HandleStream(DynamoDBEvent evnt, ILambdaContext lambdaContext)
+{
+    lambdaContext.Logger.Log($"Received {evnt.Records.Count} records");
+}
+```
+
 ## Custom Lambda Authorizer Example
 
 Lambda Annotations supports defining custom Lambda authorizers using attributes. Custom authorizers let you control access to your API Gateway endpoints by running a Lambda function that validates tokens or request parameters before the target function is invoked. The source generator automatically wires up the authorizer resources and references in the CloudFormation template.
@@ -1422,6 +1444,9 @@ parameter to the `LambdaFunction` must be the event object and the event source
     * Sets up event source mapping between the Lambda function and SQS queues. The SQS queue ARN is required to be set on the attribute. If users want to pass a reference to an existing SQS queue resource defined in their CloudFormation template, they can pass the SQS queue resource name prefixed with the '@' symbol.
 * ALBApi
     * Configures the Lambda function to be called from an Application Load Balancer. The listener ARN (or `@ResourceName` template reference), path pattern, and priority are required. The source generator creates standalone CloudFormation resources (TargetGroup, ListenerRule, Lambda Permission) rather than SAM event types.
+    * Sets up event source mapping between the Lambda function and SQS queues. The SQS queue ARN is required to be set on the attribute. If users want to pass a reference to an existing SQS queue resource defined in their CloudFormation template, they can pass the SQS queue resource name prefixed with the '@' symbol. 
+* DynamoDBEvent
+    * Sets up event source mapping between the Lambda function and DynamoDB streams. The stream ARN or table resource reference (prefixed with '@') is required.
 
 ### Parameter Attributes