doc: add action aws:ecs:stop-task for fis (#288)

Author: HarshCasper

src/content/docs/aws/services/fis.mdx

@@ -235,6 +235,7 @@ LocalStack FIS currently supports the following actions:
 - **`aws:ec2:terminate-instances`**: Runs EC2 TerminateInstances on the target EC2 instances.
 - **`aws:rds:reboot-db-instances`**: Runs EC2 RebootInstances on the target EC2 instances.
 - **`aws:ssm:send-command`**: Runs the Systems Manager SendCommand on the target EC2 instances.
+- **`aws:ecs:stop-task`**: Runs ECS StopTask on the target ECS tasks.
 
 If you would like support for more FIS actions, please make a feature request on [GitHub](https://github.com/localstack/localstack/issues/new/choose).