Add a Reference Tab to track Webform nodes.

Problem

Easy to lose track of where a webform is reference on a website.

Solution

Make it easier to track webform nodes by adding a 'Nodes' to each Webform that tracks node webform references.

Tasks

• Add 'References' tabs.
• Add help text
• Add 'Create webform' links.
• Write tests.

References

• https://www.drupal.org/docs/8/api/menu-api/providing-module-defined-actions
• https://www.drupal.org/node/2122253
• @see core/modules/field_ui/field_ui.links.action.yml

Notes

• Nodes tab will include node title, ID, #results, status, operations.
• Add 'Create webform ' link that goes to '/node/add/webform' and prepopulates webform reference.
• \Drupal\webform\Plugin\Field\FieldType\WebformEntityReferenceItem::getEntityWebformFieldName