[REQ] Elixir Package configuration

Created by: tobbbles

Is your feature request related to a problem? Please describe.

When generating an Elixir client from an OpenAPI spec, I'd like to be able to publish it to Hex, the package manager for elixir.

Currently the generated clients are unable to be published, as they are missing some required fields.

Describe the solution you'd like

I'd like for the Elixir generator to template in the needed values in mix.exs to enable publishing to Hex.

This ultimately means populating :package in project() with the following:

defp package() do
  [
    name: "{{#underscored}}{{packageName}}{{/underscored}}",
    files: ~w(lib mix.exs README* LICENSE*),
    licenses: ["{{licenseId}}"]
  ]
end

And bolstering the project definition with a :description field too.

Describe alternatives you've considered

The only alternative to render these values to is overwrite the template myself. I feel it'd be better to add this upstream.

Additional context