Formatter: Add Event to allow other modules to modify values

Please find the requested functionality implemented as per now.

As stated above, I had a hard time matching the request with the patch.
Unfortunately, the committed code is not compatible with the original patch.
I will update the issue summery, to describe the changes.

The following is reported, but in another, incorrect issue 📌 Formatter/Widget should use dependency injection instead of \Drupal calls Fixed ,
The answer would be to remove the services file. since the subscriber is to be implemented in another custom project.

I'm getting this fatal error after upgrade to 1.13

Error: Cannot instantiate abstract class Drupal\office_hours\EventSubscriber\OfficeHoursEventSubscriber in Drupal\Component\DependencyInjection\Container->createService() (line 259 of core/lib/Drupal/Component/DependencyInjection/Container.php).

This is now fixed. A new module release is created.

Automatically closed - issue fixed for 2 weeks with no activity.