allow titles for abbreviation elements

[ghost]

this allows abbreviation elements to keep their title attributes when
containing special characters.

(Originally reported on the forum)

---

• I have signed the CLA

[ghost]

I double checked this allow rule still prevents common XSS attack vectors. Like closing the title attribute and inserting an onload, or closing the element entirely and injecting a new element like script. This either omits the abbreviation element entirely or just renders some of the contents as text on the page. Harmless either way.

But now titles such as "This is a title: with a sub tile" render as expected.

[thebaer]

Awesome, thanks!