feat: Add config option to pick json library

Author: Étienne Lévesque

lib/ex_css_modules/ex_css_modules.ex

@@ -40,7 +40,7 @@ defmodule ExCSSModules do
       true ->
         (filename <> ".json")
         |> File.read!()
-        |> Poison.decode!()
+        |> json_library().decode!()
 
       false ->
         %{}
@@ -209,4 +209,6 @@ defmodule ExCSSModules do
 
   defp join_class_name([_ | _] = list), do: Enum.join(list, " ")
   defp join_class_name([]), do: nil
+
+  defp json_library, do: Application.get_env(:ex_css_modules, :json_library, Poison)
 end

mix.exs

@@ -50,7 +50,7 @@ defmodule ExCSSModules.Mixfile do
       {:excoveralls, "~> 0.14.4", only: :test},
       {:dialyxir, "~> 1.1", only: [:dev, :test], runtime: false},
       {:phoenix_html, "~> 1.0 or ~> 2.0 or ~> 3.0"},
-      {:poison, "~> 4.0 or ~> 5.0"},
+      {:poison, "~> 4.0 or ~> 5.0", optional: true},
       {:mix_test_watch, "~> 1.1", only: :dev, runtime: false},
       {:credo, "~> 1.6", only: [:dev, :test], runtime: false}
     ]