packager: proposal: adding a line in description

[emmamarichal]

Hello!

It would be great if the packager could generate the description with the to contribute link already written, instead of N/A. With this sentence: <p>To contribute, see <a href=https://github.com/RepoName/FontName">github.com/RepoName/FontName</a>.</p>

As the link of the repo is filled in the upstream.yaml, this sentence could be generated directly, right? Thanks :)