license file

[thorade]

Hi,
this is a minor suggestion: Currently, you mention the license in the Readme file only. If you instead add a license file, the repo would display the license at the side, as described here:

• https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/adding-a-license-to-a-repository
• https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository

The same is also done by e.g. Modelica standard library:
https://github.com/modelica/ModelicaStandardLibrary