Support URL autoexpanders (+, +s) work item urls

What does this MR do and why?

Adds support for work item url references and +/+s support

How to set up and validate locally

1. go to a project (I'll assume http://ee.gitlab.test:5100/flightjs/Flight/)

2. Create an new issue

3. In the issue, create a new Task (which is a work item) with the name "Sample work item". Note the URL and iid. I will assume http://ee.gitlab.test:5100/flightjs/Flight/-/work_items/42, with an iid of 42

4. Assign the Administrator to the task, and set a milestone (v4.0 in my example)

5. In a comment field, add the following markdown. Adjust the iid and urls to match what you have.

   - #42+
   - #42+s
   - http://ee.gitlab.test:5100/flightjs/Flight/-/work_items/42
   - http://ee.gitlab.test:5100/flightjs/Flight/-/work_items/42+
   - http://ee.gitlab.test:5100/flightjs/Flight/-/work_items/42+s
   - See <a href="flightjs/Flight#42">Reference</a>

6. When you Preview the comment, you should see all the expansions, it should look close to this

   

7. When you roll your mouse over the first two links, you will see that they link to flightjs/Flight/-/issues/42. This is correct, as the same reference, #42 is used for issues and work items. Clicking on the link will in fact open up the correct work item.

8. When you roll your mouse over the last items, they will link to flightjs/Flight/-/work_items/42, which is correct.

9. When hovering over each link, you should see the detailed popup.

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 #390854 (closed)