docs(events-targets): add link for Run an ECS task section (#26805)

README for aws-cdk-lib.aws_events_targets is missing the link for `Run an ECS task` section. This PR introduces the link.

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: tam0ri

packages/aws-cdk-lib/aws-events-targets/README.md

@@ -9,7 +9,7 @@ Currently supported are:
 
 * [Start a CodeBuild build](#start-a-codebuild-build)
 * [Start a CodePipeline pipeline](#start-a-codepipeline-pipeline)
-* Run an ECS task
+* [Run an ECS task](#run-an-ecs-task)
 * [Invoke a Lambda function](#invoke-a-lambda-function)
 * [Invoke a API Gateway REST API](#invoke-an-api-gateway-rest-api)
 * Publish a message to an SNS topic
@@ -416,7 +416,7 @@ rule.addTarget(
 );
 ```
 
-### enable Amazon ECS Exec for ECS Task
+### Enable Amazon ECS Exec for ECS Task
 
 If you use Amazon ECS Exec, you can run commands in or get a shell to a container running on an Amazon EC2 instance or on AWS Fargate.