fix(config): Add stage name variable to example config

example-config.sh

@@ -20,6 +20,7 @@ export COGNITO_REDIRECT_URI=# https://<Your Cognito Domain>/oauth2/idpresponse
 export BUCKET_NAME=# An S3 bucket name to use as the deployment pipeline
 export STACK_NAME=# The name of the stack to create
 export REGION=# AWS region to deploy the stack and bucket in
+export STAGE_NAME=# Stage name to create and deploy to in API gateway
 
 # Variables required if deploying a node http server
 export PORT=# <Port to start the server on>