Docs: Link to the "Conditional Tags" article in the Theme Developer Handbook from the descriptions for a variety of core conditional tag functions.

These notations largely serve to direct consumers (of both the source and the parsed code reference) to extended information on individual and related conditional tags throughout WordPress. The changeset also standardizes corresponding DocBlock summaries to use third-person singular verbs.

Notations been added for the following functions:

* comments_open()
* email exists()
* has_excerpt()
* has_post_thumbnail()
* has_tag()
* in_category()
* in_the_loop()
* is_404()
* is_active_sidebar()
* is_active_widget()
* is_admin()
* is_admin_bar_showing()
* is_archive()
* is_attachment()
* is_author()
* is_blog_installed()
* is_category()
* is_comments_popup()
* is_date()
* is_day()
* is_dynamic_sidebar()
* is_feed()
* is_front_page()
* is_home()
* is_local_attachment()
* is_main_query
* is_month()
* is_multi_author
* is_new_day()
* is_page()
* is_page_template()
* is_paged()
* is_plugin_active()
* is_plugin_active_for_network()
* is_plugin_inactive()
* is_plugin_page()
* is_post_type_archive()
* is_preview()
* is_rtl()
* is_search()
* is_single()
* is_singular()
* is_sticky()
* is_tag()
* is_tax()
* is_taxonomy_hierarchical()
* is_time()
* is_trackback()
* is_user_logged_in()
* is_year()
* pings_open()
* post_type_exists()
* taxonomy_exists()
* term_exists()
* username exists()
* wp_attachment_is_image()
* wp_script_is()

Props janalwin.
Fixes #43254.


git-svn-id: https://develop.svn.wordpress.org/trunk@42710 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.wp-scripts.php

@@ -319,8 +319,12 @@ function wp_dequeue_script( $handle ) {
 }
 
 /**
- * Check whether a script has been added to the queue.
- *
+ * Determines whether a script has been added to the queue.
+ * 
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/ 
+ * Conditional Tags} article in the Theme Developer Handbook.
+ *  
  * @since 2.8.0
  * @since 3.5.0 'enqueued' added as an alias of the 'queue' list.
  *