Add Link Type to 'add-download-link'
Since GitLab 13.1 you can add different link types to a release. This is just visual but it helps differentiate the different release assets.
Here is the API endpoint description: https://docs.gitlab.com/ee/api/releases/links.html#create-a-link
For the implemenation I guess this is the right place to do add the command line argument and this is the right place to add it to the options struct for doing the gitlab api call.
I would try to put a MR out if you don't have any objections :)