message: Add check for gd in php.yml
diff: @@ -70,6 +70,7 @@ jobs:
  - name: Testing Extensions
  run: |
  php -m
  + php -r "if(! extension_loaded('gd')) {throw new Exception('gd not found');}"
  php -r "if(! extension_loaded('xml')) {throw new Exception('xml not found');}"
  php -r "if(! extension_loaded('Xdebug')) {throw new Exception('Xdebug not found');}"
  php -r "if(phpversion()>=7.1 && ! extension_loaded('pcov')) {throw new Exception('PCOV not found');}"
  