Add a check for WP_IMPORTING before publishing or syncing

[emilyatmobtown]

Migrations and bulk CLI commands often trigger post updates. These can inadvertently trigger a publish or sync to Apple News without careful filtering. While the plugin does have filters to skip the publish/sync, a helpful enhancement would be to add a check for WP_IMPORTING before publishing/syncing. This aligns with best practices to ensure that third-party integrations are not triggered during bulk updates and it supports the developer experience by offering a simplified and universal approach.

Acceptance Criteria

• Create a filter that defaults to the value of WP_IMPORTING if it is set (or false if not) which will skip any pushes to Apple News, including article creation, updates, and deletes.
• Add a test for this new functionality.