Allow html in WordPress titles title

Add this code to functions.php file (Child Theme)

Source: https://premium.wpmudev.org/blog/wordpress-widget-title-html

function html_widget_title( $title ) {
//HTML tag opening/closing brackets
$title = str_replace( '[', '<', $title );
$title = str_replace( '[/', '</', $title );
// bold -- changed from 's' to 'strong' because of strikethrough code
$title = str_replace( 'strong]', 'strong>', $title );
$title = str_replace( 'b]', 'b>', $title );
// italic
$title = str_replace( 'em]', 'em>', $title );
$title = str_replace( 'i]', 'i>', $title );
// underline
// $title = str_replace( 'u]', 'u>', $title ); // could use this, but it is deprecated so use the following instead
$title = str_replace( '<u]', '<span style="text-decoration:underline;">', $title );
$title = str_replace( '</u]', '</span>', $title );
// superscript
$title = str_replace( 'sup]', 'sup>', $title );
// subscript
$title = str_replace( 'sub]', 'sub>', $title );
// del
$title = str_replace( 'del]', 'del>', $title ); // del is like strike except it is not deprecated, but strike has wider browser support -- you might want to replace the following 'strike' section to replace all with 'del' instead
// strikethrough or <s></s>
$title = str_replace( 'strike]', 'strike>', $title );
$title = str_replace( 's]', 'strike>', $title ); // <s></s> was deprecated earlier than so we will convert it
$title = str_replace( 'strikethrough]', 'strike>', $title ); // just in case you forget that it is 'strike', not 'strikethrough'
// tt
$title = str_replace( 'tt]', 'tt>', $title ); // Will not look different in some themes, like Twenty Eleven -- FYI: http://reference.sitepoint.com/html/tt
// marquee
$title = str_replace( 'marquee]', 'marquee>', $title );
// blink
$title = str_replace( 'blink]', 'blink>', $title ); // only Firefox and Opera support this tag
// wtitle1 (to be styled in style.css using .wtitle1 class)
$title = str_replace( '<wtitle1]', '<span class="wtitle1">', $title );
$title = str_replace( '</wtitle1]', '</span>', $title );
// wtitle2 (to be styled in style.css using .wtitle2 class)
$title = str_replace( '<wtitle2]', '<span class="wtitle2">', $title );
$title = str_replace( '</wtitle2]', '</span>', $title );

return $title;
}
add_filter( 'widget_title', 'html_widget_title' );