[Updated] Allow themes to implement hook_field_widget_multivalue_form_alter()

[joshua-graham-adelphi]

Hi GovCMS team,

We already have hook_field_widget_form_alter() implemented in theme layer via govcms.profile file.

For consistency, we should have hook_field_widget_multivalue_form_alter() implemented as well.

These hooks are related to improving editor experience.

Old request which was closed (not sure why or what plan is in place): #538

Pull request: #588

Separate issue will be made for Drupal / GovCMS 9 as hook is different.
@see https://api.drupal.org/api/drupal/core%21modules%21field%21field.api.php/function/hook_field_widget_form_alter/9.2.x

Thanks
Joshua.