Add support for Dhall

[jmgilman]

Add support for the Dhall language.

[jmgilman]

It appears that we can follow the same path taken with CUE in exporting the Nix expression JSON. This gets fed to json-to-dhall to produce a Dhall file. We could name this something static, like data.dhall, and then have downstream users ingest it into their own files (i.e. let data = ./data.dhall). Finally, convert to the desired format.

1. Export Nix expression to JSON
2. Convert JSON to Dhall
3. Import Dhall
4. Perform logic and then export to desired format (i.e. JSON, YAML, etc.)