Update docs for storybookjs#169

docs/webpack_full_control_mode.md

@@ -16,7 +16,11 @@ Example:
 // .storybook/webpack.config.js
 
 // Export a function. Accept the base config as the only param.
-module.exports = (storybookBaseConfig) => {
+module.exports = (storybookBaseConfig, configType) => {
+  // configType has a value of 'DEVELOPMENT' or 'PRODUCTION'
+  // You can change the configuration based on that.
+  // 'PRODUCTION' is used when building the static version of storybook.
+
   // Make whatever fine-grained changes you need
   storybookBaseConfig.module = { ... }
 
@@ -35,4 +39,4 @@ The following sections of the config could break storybook if deleted:
 - `config.output`
 - `config.plugins[new webpack.HotModuleReplacementPlugin()]`
 
-You've been warned.
+You've been warned.