Define creation metadata of the AppImage instance

As there can be not only one, but multiple people creating AppImage bundles for a given application software of the same application version (e.g. with certain features added/removed, using different AppImage creation systems or a different base system), it would be helpful to have some more specified metadata entries about the entity which created the given AppImage instance.

Fields which might be handy here (looking also losely at Dublin Core metadata terms):
* publisher - the person/organization which releases/offers the original AppImage instance
* creator - the person/organization who maintains the creation of the AppImage instance
* creation-date/created - the date/time on which the AppImage instance was created/build
* UUID - some id which could be used to reference a certain AppImage instance, independent of any hash-based strategy, perhaps with some semantic pattern (e.g. including string of publisher, application name, version etc.)
* generator - the software system which generated the AppImage instance, if it can be named
All such fields might be optional.

As consumer of AppImage instances such information would be handy if I am to manage multiple AppImage instance variants of some software, e.g. when testing which one works best for me.