feat(dependencies): base dependencies on plugins

Closes #3396413

src/Annotation/Source.php

@@ -25,4 +25,11 @@ class Source extends Plugin {
    */
   public $extension;
 
+  /**
+   * An array of module dependencies for this source.
+   *
+   * @var array
+   */
+  public $dependencies = [];
+
 }