Zims update script has been slightly mangled since nix-prefetch stopped working. Now it is updated to use nix-prefetch-url and no longer pulls from the Torrent sources. That script exports a regular SHA256 hash and not an SRI signature, so we now convert that to SRI as a second step in the pre-fetch pipline Also adding a cron to run the tool every month on the first, in order to keep it up to date.