Add use + var info to readme. Closes #65

Author: novaugust

README.md

@@ -152,12 +152,13 @@ For example, given the following broken code after an initial `mix format`:
 ```elixir
 defmodule MyGreatLibrary do
   @moduledoc make_pretty_docs(@library_options)
+  use OptionsMagic, my_opts: @library_options
 
   @library_options [ ... ]
 end
 ```
 
-You can fix the code by moving the static value outside of the module into a naked variable and then reference it in the module.
+You can fix the code by moving the static value outside of the module into a naked variable and then reference it in the module. (Note that `use` macros need an `unquote` wrapping the variable!)
 
 Yes, this is a thing you can do in a `.ex` file =)
 
@@ -166,6 +167,7 @@ library_options = [ ... ]
 
 defmodule MyGreatLibrary do
   @moduledoc make_pretty_docs(library_options)
+  use OptionsMagic, my_opts: unquote(library_options)
 
   @library_options library_options
 end