Elixir Planner

[Lagoja]

Summary

Add Build support and basic shell support for Elixir projects. Added this mostly as a learning exercise so I can write a short guide to creating planners in the future.

Right now, it detects Elixir projects by searching for a mix.exs file, and then creates a standalone release of the project. Resulting image size is 200MB (which is mostly Nix Packages, and seems larger than expected...)

Future Updates:

• Update the shell so that packages are installed and managed locally with Hex + Rebar
• Phoenix Framework support
• Make the image size smaller

How was it tested?

Used the test Elixir project in /testdata