Docs: Add a file header to wp-includes/class-wp-widget-factory.php, created when the `WP_Widget_Factory` class was moved to its own file in [33746].

It's important for every file in WordPress, regardless of makeup or architecture, to have its own file header, even if the file contains nothing but a class. When parsed, files and classes are mutually exclusive and should be documented with this in mind.

See [33746]. See #33413.


git-svn-id: https://develop.svn.wordpress.org/trunk@33756 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-widget-factory.php

@@ -1,10 +1,17 @@
 <?php
 /**
- * Singleton that registers and instantiates WP_Widget classes.
+ * Class file for WP_Widget_Factory
  *
  * @package WordPress
  * @subpackage Widgets
+ * @since 4.4.0
+ */
+
+/**
+ * Singleton that registers and instantiates WP_Widget classes.
+ *
  * @since 2.8.0
+ * @since 4.4.0 Moved to its own file from wp-includes/widgets.php
  */
 class WP_Widget_Factory {
 	public $widgets = array();