Versioning and Authorship for module/class/role/unit

[nxadm]

:ver<> and :auth<> (see: https://docs.perl6.org/language/typesystem#Versioning_and_Authorship) is:

• not referenced here: https://docs.perl6.org/language/modules#use
• confusingly mentioned here: https://docs.perl6.org/language/modules#is_export

To clarify the doc, we should answer these questions:

• can the adverbs ver and auth be used everywhere where a module/class/role/unit is created and consumed?
• what is the canonical source of author? Are there certain limits when creating it (does it need an email address, how must it be formatted)? When consuming it, should it refer to a github handle, CPAN user, free text as defined in the module metadata?

[coke]

here & not here appear to be the same URL

[JJ]

It's apparently not specced yet

[JJ]

It is also repeated 4 times, with slightly different and context-aware name, through the typesystem document Maybe we should remove that, since it's not specced.

[JJ]

We should also take into account rakudo/rakudo#4159: they follow the colonpair syntax.