MDL-78282 output: new sr_text renderer method

Some output classes require pre-rendered elements. In some cases, those
elements require some screen reader extra texts (especially in buttons).
The st_text method allow the outputs to create those inline tags without
using html_writer. Furthermore, the current screen reader classes are
based on bootstrap, having them isolated in renderer methods allow
themes to implement alternatives accessibility HTML structures.

lib/outputrenderers.php

@@ -3277,6 +3277,20 @@ EOD;
         );
     }
 
+    /**
+     * Outputs a screen reader only inline text.
+     *
+     * @param string $contents The contents of the paragraph
+     * @return string the HTML to output.
+     */
+    public function sr_text(string $contents): string {
+        return html_writer::tag(
+            'span',
+            $contents,
+            ['class' => 'sr-only']
+        ) . ' ';
+    }
+
     /**
      * Outputs a container.
      *

lib/upgrade.txt

@@ -53,6 +53,7 @@ information provided here is intended especially for developers.
   the page displays a heading for the activity (usually a h2 heading containing the activity name).
 * New method moodleform::filter_shown_headers() is created to show some expanded headers only and hide the rest.
 * count_words() and count_letters() have a new optional parameter called $format to format the text before doing the counting.
+* New core_renderer::sr_text method to generate screen reader only inline texts without using html_writter.
 
 === 4.2 ===