W3C Website redesign: Update to the project site; opening discussions on GitHub

For the remainder of the 2020 W3C website redesign project, we are moving to share documents by default on the W3C website redesign project mini site and marking as such any draft documents, and moving discussions to GitHub, where I will monitor and funnel questions and feedback from the W3C community to Studio 24, who work with us on this exciting project.

The Timeline page now acts as an update log for all additions and changes to the site, and its RSS feed now displays timeline entries. Changes to existing documents will be noted there (and as appropriate at the bottom of the documents themselves.)