Multiple sources in a single recipe

[mcbennet]

I was hoping to upload another S ccECP (a version 2), however, it does not appear that the git repo is set up for this kind of case (?). I assume that we would want the user to be presented with both the JCP 147, 224106 ccECP and the upcoming arxiv ccECP for sulfur after clicking 'S' in the periodic table.

If the git repo can already handle these kind of cases, can someone share a brief description of how to add another version to a given recipe.