Consider alternate structure for authorship component

[hcorson-dosch-usgs]

Currently, the authorship component (added with #15) is built using a list of primary and additional authors, each with their own specified contribution, which results in a separate contribution statement for each author. Cee points out that if multiple authors have the same contribution in this set up, the resulting text will be repetitive. Cee suggested a possible alternate structure:

Alternatively, you could split by authors and contributions instead of primaryAuthors and additionalAuthors. authors could retain names and links, and contributions captures roles and contributions. The role slot is unused, and instead could define order (i.e. project lead/lead developers first). The contributions could capture unique roles instead of unique contributors.

This would mean restructuring the component a bit, but I think we could re-use some of the same logic. One thing to keep in mind is whether we would also want one individual to be able to have multiple distinct contributions, e.g. a shared contribution of 'designed the charts', but also a solo contribution of 'created the illustrations'? I think that would be pretty simple to set up if we had a list of contributors associated with each contribution.