Support Erlang-style modules

[hissssst]

defmodule :my_module do
  use Sybil
end

Is a valid code

[vereis]

I honestly had no idea this was a thing! Thanks!

[vereis]

@hissssst feel free to just add a dialyzer ignore for that warning which breaks CI. Its happening because atom() is already covered as part of the type spec so you adding the | atom() to the module AST type causes it to overlap another @spec declaration.

I've generally always liked to keep multiple specs despite the fact that these get collapsed into one spec by dialyzer for clearer documentation purposes, so I'm not too worried about the domain overlap here.

If possible, we can just disable the check for this one file, but if need be, feel free to set it in mix.exs