Add URL for service families

It would be nice to have a URL under which you can find all badges of a specific service like we currently for categories e.g. https://shields.io/service/pypi. This would allow sites to Link directly to shields.io (Check out our badges on shields.io).

Start by inspecting the existing category URL at https://shields.io/service/pypi and how its badges are selected. The work is done when each service family has a direct URL that lists its badges and can be linked from external sites.

Written by the indexing model from the issue text.