Media: Accessibility: Make alt text information URL translatable.

Allow translators to replace the W3C WAI decision tree link used to provide information about writing alt text. Improves accessibility for non-English speaking content authors.

Props tmatsuur, joedolson, oglekler, SergeyBiryukov, myhro, sabernhardt.
Fixes #60975.

git-svn-id: https://develop.svn.wordpress.org/trunk@58240 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/media.php

@@ -3241,7 +3241,8 @@ function edit_form_image_editor( $post ) {
 		printf(
 			/* translators: 1: Link to tutorial, 2: Additional link attributes, 3: Accessibility text. */
 			__( '<a href="%1$s" %2$s>Learn how to describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
-			esc_url( 'https://www.w3.org/WAI/tutorials/images/decision-tree' ),
+			/* translators: Localized tutorial, if one exists. W3C Web Accessibility Initiative link has list of existing translations. */
+			esc_url( __( 'https://www.w3.org/WAI/tutorials/images/decision-tree/' ) ),
 			'target="_blank" rel="noopener"',
 			sprintf(
 				'<span class="screen-reader-text"> %s</span>',

src/wp-includes/media-template.php

@@ -159,7 +159,8 @@ function wp_print_media_templates() {
 	$alt_text_description = sprintf(
 		/* translators: 1: Link to tutorial, 2: Additional link attributes, 3: Accessibility text. */
 		__( '<a href="%1$s" %2$s>Learn how to describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
-		esc_url( 'https://www.w3.org/WAI/tutorials/images/decision-tree' ),
+		/* translators: Localized tutorial, if one exists. W3C Web Accessibility Initiative link has list of existing translations. */
+		esc_url( __( 'https://www.w3.org/WAI/tutorials/images/decision-tree/' ) ),
 		'target="_blank" rel="noopener"',
 		sprintf(
 			'<span class="screen-reader-text"> %s</span>',