Site Health: Allow attachments to be added to recovery mode emails.

The `wp_mail()` function has the ability to add attachments to emails. There is currently no way to add attachments to the recovery mode email sent out to site admins when a PHP error is encountered on their site.

This change adds that ability through the use of the `recovery_mode_email` filter, allowing developers to use the full capabilities of `wp_mail()`.

Props desrosj, timothyblynjacobs.
Fixes #51276.
Built from https://develop.svn.wordpress.org/trunk@48964


git-svn-id: http://core.svn.wordpress.org/trunk@48726 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-recovery-mode-email-service.php

@@ -199,6 +199,7 @@ When seeking help with this issue, you may be asked for some of the following in
 			'subject'     => __( '[%s] Your Site is Experiencing a Technical Issue' ),
 			'message'     => $message,
 			'headers'     => '',
+			'attachments' => '',
 		);
 
 		/**
@@ -213,6 +214,7 @@ When seeking help with this issue, you may be asked for some of the following in
 		 *     @type string       $subject     Email subject
 		 *     @type string       $message     Message contents
 		 *     @type string|array $headers     Optional. Additional headers.
+		 *     @type string|array $attachments Optional. Files to attach.
 		 * }
 		 * @param string $url   URL to enter recovery mode.
 		 */
@@ -222,7 +224,8 @@ When seeking help with this issue, you may be asked for some of the following in
 			$email['to'],
 			wp_specialchars_decode( sprintf( $email['subject'], $blogname ) ),
 			$email['message'],
-			$email['headers']
+			$email['headers'],
+			$email['attachments']
 		);
 
 		if ( $switched_locale ) {

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-alpha-48963';
+$wp_version = '5.6-alpha-48964';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.