Develop system for attributing contributors

[ehwenk]

We should come up with a systematic way to attribute people who've contributed ideas or coding to a GitHub commit.

Right now, we add each other as co-authors if we've co-contributed code to a branch/commit, but don't have a system for other contributors.

In two recent commits I mentioned others (commit 0b04d61; seed trait workshop outcomes; commit e5e1b0d; seed mass errors that Isaac Towers noticed), but we should have a more consistent system for where this information is stored.

For instance, maybe a standalone section of the document, or where we list contributions / funding etc.

In addition mentioning the people with either their GitHub name (@...) or simply their name in commits should become standard practice.