Update Sponsors page with "Google Season of Docs" entry

Can we have Google Season of docs added as a sponsor here: ​https://www.torproject.org/about/sponsors/?

Logo should come from this page: ​https://developers.google.com/season-of-docs/docs/press Link should point to ​https://developers.google.com/season-of-docs/ Text for sponsor can be taken from the "Email template for inviting technical writers to apply for Season of Docs" in the Promotion and press page (​https://developers.google.com/season-of-docs/docs/press), e.g:

"Season of Docs (g.co/seasonofdocs) is Google's annual program that fosters collaboration between open source projects and technical writers.

Season of Docs is a unique program that pairs technical writers with open source mentors to introduce the technical writer to an open source community and provide guidance while the writer works on a real world open source project. The technical writer in turn provides documentation expertise to the open source organization."

Imported from: https://trac.torproject.org/projects/tor/ticket/30412