Issue #3: Switch image style warmer to queue:process, shows remaining #.

.do/run-background-tasks.php

@@ -25,7 +25,7 @@
 // Every 5 minutes, process jobs from the image style warmer.
 $loop->addPeriodicTimer(300, function() use ($drush): void {
  (new WorkerProcess(
- $drush . ' queue:run image_style_warmer_pregenerator --verbose'
+ $drush . ' queue:process image_style_warmer_pregenerator'
  ))->start();
 });