WP External Link Icon

functions.php:
---------------
```
add_filter('the_content', 'external_links_nofollow_blank');
function external_links_nofollow_blank($content) {
    $content = preg_replace_callback('/]*href=["|\']([^"|\']*)["|\'][^>]*>([^<]*)<\/a>/i', function($m) {
        if (strpos($m[1], home_url()) === false)
            return 'href="'.$m[1].'" rel="nofollow" data-external="true" target="_blank">'.$m[2].'</a>';
        else
            return 'href="'.$m[1].'">'.$m[2].'</a>';
    }, $content);
    return $content;
}
```

style.css:
-----------
```
a[data-external="true"]{
    position:relative;
}
a[data-external="true"]::after{
    content:'';
    background-image: url('images/external-link.svg');
    background-position: center;
    background-repeat: no-repeat;
    background-size: 20px 20px;
    width:20px;
    height:20px;
    display:inline-block;
    position:relative;
    left:1px;
    top:6px;
}
```

svg:
-------
```
<svg width="50px" height="50px" viewBox="0 0 50 50" xmlns="http://www.w3.org/2000/svg"><path d="M38.288 10.297l1.414 1.415-14.99 14.99-1.414-1.414z"/><path d="M40 20h-2v-8h-8v-2h10z"/><path d="M35 38H15c-1.7 0-3-1.3-3-3V15c0-1.7 1.3-3 3-3h11v2H15c-.6 0-1 .4-1 1v20c0 .6.4 1 1 1h20c.6 0 1-.4 1-1V24h2v11c0 1.7-1.3 3-3 3z"/></svg>
```