Wordsafe truncation breaks if last occurrence of the delimiter is inside a tag

For example:

```php
$string = 'Hello world <a href="#" rel="nofollow">link</a>';

echo (new Marcgoertz\Shorten\Shorten())->truncateMarkup($string, 14, '...', true, true);
```

```
Hello world <a href="#"...</a>
```