Add "contribute" to the header

[MBAbrams]

so it would read: About, Data Sources, Categories, Contribute, and Documentation.
There are 3 ways to contribute: Directly in Github, send an e-mail, or edit text

[wawong]

Tom, can you provide a paragraph about how to contribute to KS using these three methods? So that, I can create a "contribute" page.

[tgbugs]

I think Maryann has a google doc for at least one of these. I will write up a markdown doc that has what we need. Where should I put it?

[wawong]

HI Tom,

Can you give me the permission to that google doc?

Thanks!

[tgbugs]

Done.