Update to the CC BY-SA 4.0 license

[lkocman]

Project mentions all content in is licensed under CC-BY-SA 3.0 unless otherwise stated.

SUSE Open Source policy currently recommends CC BY-SA 4.0 for new docs && artwork

Do we want to re-consider license of the repo?

Success story from wikipedia
Wikipedia's update to the CC BY-SA 4.0 license, from the previous CC BY-SA 3.0 license, helps to make the project more accessible, globally compatible, simplified, and readable. For years, new knowledge created under the 4.0 license could not be directly added to Wikipedia

Thank you