Automatic checks for missing license headers

[armintaenzertng]

There is currently no tool in the CI that checks each file for a correct license header. We should introduce such a check, for example by using reuse.

[goneall]

Just for reference, this was an Google Summer of Code project to perform a similar function. It is no longer being maintained and is archived here: https://github.com/spdx/license-coverage-grader

[harshkasat]

Hey there! I am a beginner. Can you guide me on how to resolve this issue? Do we have to run an auto-check test?