chore(scaffolding): update docs (#336)

SCAFFOLDING.md

@@ -28,7 +28,7 @@ To create an `addon`, you must create a [`yeoman-generator`](http://yeoman.io/au
 Objects are made using strings, while strings are made using double strings. This means that in order for you to create an string, you have to wrap it inside another string for us to validate it correctly.
 
 
-### `opts.env.configuration`(Required)
+### `opts.env.configuration`(required)
 
 Initialized inside the constructor of your generator in order for the CLI to work.
 
@@ -84,3 +84,13 @@ If you want to name your `webpack.config.js` something special, you can do that.
 ```js
 this.options.env.configuration.dev.configName = 'base';
 ```
+
+### `writing` (required)
+
+For the scaffolding instance to run, you need to write your configuration to a `.yo-rc.json` file. This could be done using one of the lifecycles in the yeoman generator, such as the `writing` method.
+
+```js
+writing() {
+	this.config.set('configuration', myObj)
+}
+```