Add alternative display for teacher profile picture

When displaying teacher profile picture on course information, an
alternative display (for
accessibility) was missing. The alternative text "[TEACHE NAME]
Profile" is set.

main/auth/courses_categories.php

@@ -307,7 +307,7 @@ function returnThumbnail($course)
         }
         $name = $value['firstname'].' ' . $value['lastname'];
         $html .= '<a href="'.$value['url'].'" class="ajax" data-title="'.$name.'">
-                <img src="'.$value['avatar'].'"/></a>';
+                <img src="'.$value['avatar'].'" alt="'.$name.' ' .get_lang('Profile').'"/></a>';
         $html .= '<div class="teachers-details"><h5>
                 <a href="'.$value['url'].'" class="ajax" data-title="'.$name.'">'
                 . $name . '</a></h5></div>';