Add config schema

On updating the module and performing a

drush updb

I get the following error

 ------------------ ----------- --------------- ----------------------------------------------
  Module             Update ID   Type            Description
 ------------------ ----------- --------------- ----------------------------------------------
  required_by_role   8001        hook_update_n   8001 - Clean up the required_plugin_options.
 ------------------ ----------- --------------- ----------------------------------------------


 // Do you wish to run the specified pending updates?: yes.

>  [notice] Update started: required_by_role_update_8001
>  [error]  array_filter(): Argument #1 ($array) must be of type array, int given
>  [error]  Update failed: required_by_role_update_8001
 [error]  Update aborted by: required_by_role_update_8001
 [error]  Finished performing updates.

dieterholvoet → changed the visibility of the branch 2.0.x to hidden.

That's weird, the plugin options are supposed to be arrays. I don't see how they could be an integer. I'll change the update hook to discard any non-array plugin options, since they don't carry any meaning anyway.

I started a MR, let me know if it fixes your issue.

Your MR worked and no errors.