[interpeer] Vessel draft specification

Hi all, as I previously wrote, we're using https://specs.interpeer.io as the home for our specifications now. The first draft is now sufficiently complete that feedback is welcome; you can find it at https://specs.interpeer.io/draft-jfinkhaeuser-vessel-container-format/ Note that the corresponding code project at https://codeberg.org/interpeer/vessel does not yet implement the specification; rather it provides a starting point. Finishing this implementation my focus for the coming weeks. I hope it's understandable; let me know if there are questions. Enjoy! Jens