Add special styling to "Introduced in" notes

Add new filter to find all "Introduced in" occurrences and style them.

How it works

The filter works on the built HTML, so it uses the following regex https://rubular.com/r/m6Bu173t5cmroD

(<a href=".*">)?Introduced(<\/a>)? in

which captures the case where "Introduced" is a link and the case where it's not.

When it's found, it replaces <blockquote> with <introduced-in>.

Changes

Former style, before the change

Updated according to the feedback

• Single-line notes:

http://style-introduced-in-notes.178.62.207.141.xip.io/ee/user/group/epics/:

• Multiple-line notes:

http://style-introduced-in-notes.178.62.207.141.xip.io/ee/user/project/pages/:

Related issues

Closes https://gitlab.com/gitlab-com/gitlab-docs/issues/370