Add local test with SAM CLI in the README

Author: bnusunny

examples/remix/README.md

@@ -78,3 +78,13 @@ $ docker run -d -p 3000:3000 {ECR Image}
 ```
 
 Open web browser to visit `http://localhost:3000/`
+
+## Local test with SAM CLI
+
+In general, you can test your web app locally without simulating AWS Lambda execution environment. But if you want to simulate Lambda and API Gateway locally, you can use SAM CLI.
+
+```shell
+sam local start-api --warm-containers EAGER --region us-west-2
+```
+
+This command will start a local http endpoint and docker container to simulate API Gateway and Lambda. Please modify the region to match the actual region you are using. You can test it using `curl`, `postman`, and your web browser.