Title shortcode - Use "search title" when in a `is_search()` condition

[DamChtlv]

In this code:

PiloPress/includes/classes/admin/editor/class-shortcodes.php

Lines 184 to 187 in ff1e79e

	// Front
	if ( is_singular() ) {

Should take example of the wp_get_document_title() function code for this shortcode:

• https://developer.wordpress.org/reference/functions/wp_get_document_title/#source

Have something like:

if ( is_search() ) {
    $title = sprintf( __( 'Search Results for “%s”' ), get_search_query() );