50ba797 ci: trigger differential-shellcheck workflow on push

Authored and Committed by jamacku a year ago
    ci: trigger differential-shellcheck workflow on push
    
    Also update `differential-shellcheck` to latest version - https://github.com/redhat-plumbers-in-action/differential-shellcheck/releases
    
    Fixes: https://github.com/redhat-plumbers-in-action/differential-shellcheck/issues/215