Add Config Split Specifications to Drupal Spec tool

[allierays]

Config split is common on most complex Drupal builds. We should include this in the Drupal Spec tool with automated tests as a separate tab.

[allierays]

Please assign to me so I can work on this when you have a chance. Thanks!!

[TravisCarden]

Here you go, @allierays. I look forward to seeing what you come up with!