docs: update legal documents

[tomaszbarwicki]

Description

Updates due to changes in TRG 7:

• added Terms of Use in CONTRIBUTING file
• extended NOTICE file with a notice for the CC-BY-4.0 license
• added the CC-BY-4.0 license to the root repository as default license for non-code artifacts

fixes #34

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files

[FaGru3n]

LGTM

[carslen]

The rendering will be hard to read, because the linebreaks are ignored in Markdown. So I added new Subheadings and added some more line breaks for readability in my suggestion.

[tomaszbarwicki]

Created another PR to fix Quality Checks non root container failure - #36