Support cpanfile and cpanfile.snapshot

[andrew]

TIL via #1019 that Perl has more ways of specifying dependencies, namely cpanfile and cpanfile.snapshot using https://github.com/perl-carton/carton, we should add support to https://github.com/librariesio/librarian-parsers and https://github.com/librariesio/bibliothecary for them.

Example files:

• https://github.com/mysociety/fixmystreet/blob/master/cpanfile
• https://github.com/mysociety/fixmystreet/blob/master/cpanfile.snapshot

More details on spec: https://metacpan.org/pod/cpanfile

[andrew]

Moving this to the Backlog as we'd still like to implement it but can't see that happening in the near future.

[zmughal]

I can help implement this. Would I need to submit against bibliothecary? The simplest approach would be to use Module::CPANfile and Carton::Snapshot::Parser from CPAN. These can be put in scripts that are called.