[FEATURE] Add license option to steps

[mteu]

Is your feature request related to a problem?

The current version defaults to GPL 2.0 which is common and should be kept as the default license. However, it would come in handy if users where to be able to select GPL 3.0, too. In that case the corresponding LICENSE file should be generated and the composer.json should be updated accordingly.

Describe the solution you'd like

This all will be possible with the target file support that will be introduced with CPS-IT/project-builder#54. This PR anticipates the release incorporating that new feature.

Describe alternatives you've considered

No response

Additional context

No response