preg_replace is deprecated - (my solution)

[aonzzung]

Hi there,

I found that preg_replace is deprecated warning is showing on sidebar.
So, here is what I modified the code to fix deprecation issue.
You can also commit my solution below.

functions.php

// filter tag clould output so that it can be styled by CSS
function wp_bootstrap_add_tag_class( $taglinks ) {
    $tags = explode('', $taglinks);
//    $regex = "#(.*tag-link[-])(.*)(' title.*)#e";
    $regex = "#(.*tag-link[-])(.*)(' title.*)#";
    
    foreach( $tags as $tag ) {
//      $tagn[] = preg_replace($regex, "('$1$2 label tag-'.get_tag($2)->slug.'$3')", $tag );
        $tagn[] = preg_replace_callback($regex, function ($matches) {
            return $matches[1].$matches[2].' label tag-'.get_tag($matches[2])->slug.$matches[3];
        }, $tag );
        
    }

    $taglinks = implode('', $tagn);

    return $taglinks;
}

[chrisbarnes]

@aonzzung can you submit a pull request with this?