Add option to generate web issue links on JIRA tickets.

[chrisperelstein]

It'd be nice if there was an option to generate a web issue link on JIRA tickets that links to the commit (and merge request when that's supported). This would allow a nicer way for people to see related commits/merge requests.

info on issue links:
https://confluence.atlassian.com/jiracoreserver073/linking-issues-861257339.html

api for dealing with issue links:
https://developer.atlassian.com/server/jira/platform/jira-rest-api-for-remote-issue-links/