Upload Jira Connect app descriptor to Atlassian Marketplace

Follow-up from https://gitlab.com/gitlab-org/gitlab-ee/issues/9641 and https://gitlab.com/gitlab-org/gitlab-ee/issues/9643

We need to create an account and upload a static version of the app descriptor defined in JiraConnect::AppDescriptorController.

This allows our app to be added to the Atlassian Marketplace.

URLs here should point to GitLab.com