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 :)
I see :)

Functions in `function-html.php` are outputting content in an HTML web page context and that content needs to be escaped (for instance to make sure a title containing `this is a <script>` ends up being displayed as `this is a &lt;script&gt;` and not interpreted as a javascript snippet)

Content produced by the API functions shall not be escaped, it's raw content. Hence, `$title = yourls_get_keyword_title( $keyword );` only.