stackql-exec action pass variable to iql file

[yunchengyang515]

https://stackoverflow.com/questions/2914220/bash-templating-how-to-build-configuration-files-from-templates-with-bash/11050943#11050943

[jeffreyaven]

closed with #14, supports ext vars using inline jsonnet see : https://github.com/stackql/stackql-exec/blob/main/.github/workflows/stackql-exec.yml#L58 and https://github.com/stackql/stackql-exec/blob/main/stackql_scripts/google-instances-by-status-with-vars.iql