Export metadata to output directory

[pdiakumis]

Upon writing the tidy files, also write an e.g. nemo_metadata.json file with information about the nemo version and the input directory path. Maybe even write the full command used.

[reisingerf]

Sounds like a good idea!
Are you considering to generate / add a unique execution ID (preferably ULID) to this metadata.json?
(I think this could be very useful)