Write MANIFEST.txt files

[holtgrewe]

Is your feature request related to a problem? Please describe. We currently have no good way of ensuring downloaded data is correct.

Describe the solution you'd like We should write out MANIFEST.txt files in the same way that we do for annonars-data-clinvar.

Describe alternatives you've considered N/A

Additional context

• https://github.com/varfish-org/annonars-data-clinvar/pull/82