Way to list a packs public constants

[stevegeek]

Hey all! packwerk/packs and related tools are really great, thanks!

There is now a new way to specify public constants using the sigil # pack_public: true.

However this approach suffers a discoverability problem for devs looking at a pack to see what it exposes.

With the app/public directory it's straight forward to see what a pack exposes.

It is also pretty clear to see in the proposal in #36 with the public_constants: in package.yml.

However the sigil approach is a bit trickier.

Unless there is already a way to see this that I missed, it would be cool to have a command on packs (or extra output on packs get_info) that lists out the publicly exposed constants for a given pack.

(random extra thought, maybe get_info command could be renamed to just info)