idea: migrate `examples` directory to a `hs-to-coq` registry of supported modules

[quinn-dougherty]

Desired behavior

Maybe a direction the cli could go in would look like the following:

if containers is specified in some config file, then hs-to-coq goes to some central hub or registry where coqified containers lives and pulls it down.

This could be approached one of two ways

1. make hs-to-coq talk to the internet
2. have a broader make or nix context talk to the internet on behalf of hs-to-coq

complication: versions

A really ideal execution of this would allow for config file to specify different versions of containers, so in the registry would live coqifications of a number of supported versions. More of a stretch goal.

See also https://github.com/plclub/hs-to-coq/issues/196