chore: use license-checker to enforce license compliance

[bufferoverflow]

Checklist

• [x] I've read and followed the Contribution Guide.
• [x] My commit messages reference affected issues and mention breaking changes if applicable.
• [ ] I've updated / wrote inline documentation for the source code affected by my changes.
• [ ] All mandatory CI checks have passed (see when Pull Request has been submitted).

Open Question

What does this Pull Request do

• use license-checker to enforce license compliance
• enforce used licenses to comply with headerless.org, see https://github.com/headerless/headerless/issues/7
• related issues #85 #88 #91