Add a new Content Tag: {title_attr}

[cabrerahector]

Is your feature request related to a problem? Please describe.

Currently the plugin provides two title related Content Tags:

• {title} which returns a link to the post using the title as text.
• {text_title} returns the post title alone, no text.

Problem is that if the user uses the latter inside a title attribute or an alt attribute, if the title contains single/double quotes it might break the HTML markup of the tag and could cause some issues on the page itself.

Describe the solution you'd like

A new {title_attr} Content Tag that would behave just like {text_title}, except it's sanitized for usage inside tag attributes.