Add title to returned values from yourls_api_expand

Seem a bit of overkill to write a whole new plugin just to add "title" into returned results, and I'm sure I'm not the only one who would like the title of an expanded URL from the API. So I'm proposing this commit :)
Same reason you have it here, I suppose?
https://github.com/YOURLS/YOURLS/blob/master/includes/functions-html.php#L453
In other words, I don't know, I just copied the way you'd done it.
So, why ```htmlspecialchars()``` ? :)