use initial tag if not deployed to an environment yet (#35)

## Summary

- Routine Change

### Details

- use an initial tag if its not been deployed to an environment yet

Author: anthony-nhs

.github/scripts/get_target_deployed_tag.sh

@@ -2,4 +2,10 @@
 
 current_deployed_tag=$(aws cloudformation describe-stacks --stack-name fhir-validator --query "Stacks[0].Tags[?Key=='version'].Value" --output text)
 
+
+if [ -z "$current_deployed_tag" ]
+then
+     current_deployed_tag=v1.0.30-alpha
+fi
+
 echo "CURRENT_DEPLOYED_TAG=${current_deployed_tag}" >> "$GITHUB_ENV"