Just check if build_json_task is not nil

If the task does not exist, a compilation error will be thrown.

Author: EasterPeanut

lib/ex_css_modules/ex_css_modules.ex

@@ -44,7 +44,7 @@ defmodule ExCSSModules do
           |> File.read!()
           |> json_library().decode!()
 
-        not is_nil(build_json_task) ->
+        build_json_task ->
           with {:ok, json_filename} <- build_json_task.run(filename: filename) do
             json_filename
             |> File.read!()

lib/ex_css_modules/view.ex

@@ -11,7 +11,7 @@ defmodule ExCSSModules.View do
   also be enabled through the `:embed_by_default` config option.
 
   If adds the following functions to the View:
-  - stylesheet/0 - same as ExCSSModules.stylesheet/1 with the stylesheet predefined
+  - stylesheet/0 - same as ExCSSModules.stylesheet/2 with the stylesheet predefined
   - class/1 - same as ExCSSModules.class/2 with the stylesheet predefined
   - class_name/1 - same as ExCSSModules.class_name/2 with the stylesheet predefined
   - class_name/2 - same as ExCSSModules.class_name/3 with the stylesheet predefined