allow authors to be a TOML array

[simonbyrne]

Fixes #3705.

[fredrikekre]

Are there any consumers of this information?

[simonbyrne]

https://github.com/KlausC/PkgVersion.jl is the only package I am aware of (and that just returns the value)

[simonbyrne]

For reference, GitHub suggests people use the CITATION.cff format, which also provides a richer schema:
authors can be either a person or entity

The main differences are:

• orcid is the full URL, not just the 16-digit id (which probably makes sense, as it is easier to copy-paste)
• website instead of url (I don't have strong opinions)
• name is only for entities, persons instead use family-names,given-names, etc. This is the only one which is a bit sticky, but we could probably just allow either (or both)?

I'd prefer not to reinvent the wheel, so would be happy to just defer to them, with the modification that users can choose to provide just name if they would like to.

[simonbyrne]

One minor advantage of using given-names/family-names is that it matches the Zenodo fields.