Technically since Reference Application is bundling releases of other software, I wouldn’t put the requirement on you to write the release notes for those modules but ideally you would be linking to published release notes within each module’s documentation. (Remember that there’s no requirement that an add-on module in the OpenMRS ecosystem use our JIRA system for issue tracking.) Maintaining release notes (and other documentation) is something that each module maintainer really should be doing on their own.
But regarding the type of link you provided above, all you need to do is add it as you would a regular link. Highlight the text to be linked and provide that URL as the target using the link icon button in the editor, and then the URL in the target field of the “Web Link” tab.
(Of note, the URL you provided doesn’t actually list any issues assigned to those fixVersions.)
If you need to select a set of issues that are not constrained to a JIRA Project, you’ll have to use something like labels I think, and then create a search for issues that have that label and constrain them.