hard coded license needs to be dynamic

https://gitlab.dkrz.de/ch1187/plugins4freva/freva-plugin-template/-/blob/main/%7B%7Bcookiecutter.plugin_slug%7D%7D/pyproject.toml?ref_type=heads#L32

In pyproject.toml, license is hard coded to EUPL which needs to be dependent on the user's license choise.