nit! pod and whitespace
add GHA to make one-liners easier

...while discouraging its use for anything *but* one-liners at the CLI.
POD updates
_next() now supports arbitrary params

...that will be included in the returnd blessed hashref.
switch to utf8-safe json decoding
refactor _get for better error handling and _get_single()

...this might get refactored some more, and certainly will when we go over to
using the error-checking parts for the other calls.  ...and if we decide to
name them differently.
add repo fork predicates and collector
add token_owner, api slots

We may want to set the ```user``` slot to someone else (e.g. someone else's repo (or
fork, etC) that we're looking at) such that things Just Work.  It might also
be useful to retain who actually owns the token...  So that's stashed away
independently in ```token_owner``` at construction time.

We also stash a ref to the original instance returned by GitHub::API->new() in
the ```api``` slot, just in case we need it for something new.
tweak user(), org() to pass on extra args and handle named users
tweak how we generate our agent string

e.g. "devel" when in devel (no $VERSION)
forks() now returns an array ref of Repo instances
last released version's README