Improve Connect Application Docs

Problem to solve

Currently, we do not have dedicated documentation about the GitLab for Jira Connect application on https://docs.gitlab.com/ee/user/project/integrations/jira.html . The documentation is on the Jira Development Panel docs page, which isn't the right home for this: https://docs.gitlab.com/ee/integration/jira_development_panel.html#gitlabcom-1

We should move that and reorganize in a more sensible place to make it easier for users to find. To be frank, aside from Googling it, I'm not even sure where the DVCS connector page is linked from.

Additionally, the listing page on the Atlassian Marketplace isn't clear enough, and could better reflect that content as well. Tracking work for that can be done in this issue.

Further details

Proposal

Who can address the issue

Other links/references