LICENSE: consider licensing material on website under CC license

[kortschak]

Currently we essentially don't license any material on the website. The BSD license is not really right for prose, so the closest license is probably CC-BY-SA (https://creativecommons.org/licenses/by-sa/4.0/)

Are the current authors OK with that?

[kortschak]

That should have been /cc @btracey @sbinet. I'll do the work if you are both OK with it.

[sbinet]

+1