D6972: Add CC BY-SA 4.0 International and set it as default

[Luigi Toscano]

ltoscano requested review of this revision.

REPOSITORY
  R238 KDocTools

REVISION DETAIL
  https://phabricator.kde.org/D6972

To: ltoscano, jriddell
Cc: jriddell, lueck, #frameworks, #documentation, skadinna