Plugin list only shows the first author

When authors are comma separated, like this: `Lifeyouristhis, Timeout`

The website only shows the first name:

Relevant Code:
https://github.com/endless-sky/endless-sky.github.io/blob/d71ddddf0540a31a2e32926ce86a5d8610c7bec0/plugins.html#L122-L127

Apparently I wrote this, but I really don't know why. I guess at some point I was expecting `authors` to also be an array? As it stands, all calls go through L125, where any author beyond the first are cut off.

Ref https://github.com/endless-sky/endless-sky-plugins/pull/1887