Save version of ELN-software

[SteffenBrinckmann]

What do you think of adding the version number of the ELN-software to everybody's favorite "sdPublisher" entry. That way, importing can differentiate if the structure ever changes upon an ELN update.
As far as I understood, the parent 'version' specifies that we use an ro-crate in version 1.0, which in version 2.0 might become an xyz format.

[NicolasCARPi]

sdPublisher takes a Person or Organization is types, and they don't have versions.

What I suggest is to use version for the eln version, and schemaVersion for the ro-crate version (even if it is already present in the conformsTo and @context, it doesn't hurt to add it there for easy grabs.

The eln crate version should be semver, but it shouldn't be the same as the software itself. Because <ELN> can update from v3 to v4 without changing the .eln output. So it should only be bumped when the crate format changes.