Write update hook to add config install schema

I've added the mentioned update hook and also default configuration yml.

The update hook was setting the default value to null, not empty string, it needs to be empty string, so updated that part of the code. In my POV can be merged, but because my change was last I'll leave it to needs review. The 📌 Automated Drupal 10 compatibility fixes Fixed needs to be merged for test for D10 to pass, the config install is also added there.

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