Add dir2json, improve the command line experience, change README, etc.

[alurm]

We want to add dir2json (somehow), so it's possible to pack directories into JSON.

Currently, we have only json2dir. It accepts no arguments, very simple.

Besides dir2json, I have a couple of features in mind:

• List JSON archives in various ways:
  • Something like ls is currently possible by passing the archive to jq keys[] -r
  • Something like find . is currently possible by passing the archive to jq 'walk(if type != "object" then null end) | paths | join("/")' --raw-output (or --raw-output0) (thanks @magistau)

I'm thinking of the following CLI:

# Usage.
jsondir

# Basic functionality.
jsondir to json
jsondir to dir

# Listing.
jsondir list
jsondir find

# If we decide to support YAML.
jsondir to yaml
jsondir to dir from yaml
jsondir list yaml
jsondir find yaml

Other options

dir2json
json2dir

Unclear how to add subcommands

---

jsondir json create
jsondir dir create
jsondir json list <path>
jsondir json paths <path>

Too verbose?

---

json2dir
json2dir unpack # (Explicit.)
json2dir pack

It's confusing how json2dir can actually create JSON.

[magistau]

Somewhat related: dj command name isn't taken by any package in my local nix-index and it sounds cool, maybe use that