chore: use license-checker to enforce license compliance

[bufferoverflow]

Checklist

• I've read and followed the Contribution Guide.
• 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 using headerless code correctly headerless/headerless#7
• related issues WIP: Chore/license compliance #85 [WIP] docs(readme): add Headerless.org badge #88 Check compliance with Core Infrastructure best practises #91