Add defmodule to order of module contents

Author: Odaeus

README.md

@@ -835,7 +835,7 @@ generally preferred practice.
  1. `@callback`
  1. `@macrocallback`
  1. `@optional_callbacks`
- 1. `defmacro`, `defguard`, `def`, etc.
+ 1. `defmacro`, `defmodule`, `defguard`, `def`, etc.
 
  Add a blank line between each grouping, and sort the terms (like module names)
  alphabetically.