Update README.md

Author: lmangani

lambda/README.md

@@ -8,6 +8,19 @@
 
 > Let's run chdb in a lambda function for fun a profit!
 
+## Local Image Test
+Build and run the Lambda locally:
+```
+docker build -t chdb:lambda
+docker run -p 9000:8080 chdb:lambda
+```
+
+Validate the API using curl
+```
+curl -XPOST "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{"query":"SELECT version()", "default_format":"JSONCompact"}'
+```
+
+
 ## Upload Docker image on ECR and Lambda
 Lambda function continers must be hosted on the AWS Elastic Container Registry.