Support expanded reference formats for URLs

What does this MR do and why?

This is a follow-up to !74369 (merged) to allow the same feature on URL references.

This allows appending a + to issue, MR, and epic URL references so that their title is rendered in the HTML

Screenshots or screen recordings

Screen_Recording_2021-12-02_at_7.51.41_PM

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #15694 (closed)