x-publish generated sources README content also to whosonfirst.org

[nvkelso]

A condensed version of https://github.com/whosonfirst/whosonfirst-sources/blob/master/sources/README.md should probably go here: https://whosonfirst.org/docs/licenses/. Probably requires work in this repo and the www repo.

Proposed condensed text:

• Alameda County Data Sharing Initiative under Public Domain license used for property, geometry. Sourced from https://data.acgov.org/.

Where we link to the sources repo README into for that full source name, list the license type, list the usages, and provide link back to original data (whatever is in our src json, which is often a general landing page and sometimes a specific download page).