Google Docs/Sheets support

[critmcdonald]

The object of this issues is two fold:

This may be an over-complicating feature, or perhaps a different template, but the idea is this:

• To be able to use Google Sheets as content for tabular data and key-value pairs.
• A given page in the project could be linked to Google Doc. That Doc would have front matter (preferably ArchieML). The text would be Markdown.

There are two npm packages that I think will do the trick for me:

• doc-to-archieml
• sheet-to-data

I've added them to the googledocs branch of this repo, but I don't know how to hook them up. I have figured out how to do the google auth based on NPRs interactive temlplate that I think will work, but ...