Address conflict with Features over config.installer class

Added a PHPUnit test, however it requires a composer.json to add dev dependencies (features.)

The two composer jobs are failing due to the lack of a Drupal 11 compatible version of features.
Personally, I think having the ability to test interoperability between this module and features is valuable, however if features doesn't create a compatible release, we'll be stuck with broken jobs.

We could consider just copying the parts of features we need to test into our test module.

trackleft2 → changed the visibility of the branch 3.0.x to hidden.

I know this was just flagged, but we're having a conflict with Features over config provider 3.0.0-alpha3

Hey there @anicho01 I've updated the merge requests, however it is difficult to test without a Drupal 11 compatible version of features...

@trackleft2 this issue occurs (and I assume can be tested) when using the Features D11 compatibility fork

https://git.drupalcode.org/issue/features-3447460