Merge pull request #1496 from stealjs/env2

Document possible values of steal.loader.env

docs/config-env.md

@@ -23,3 +23,13 @@ steal.loader.isPlatform("window"); // true
 ```
 
 Rarely do you need to set `env` any more, more likely you want to use [config.loadBundles]. env is set by plugins in most cases.
+
+## Common values
+
+A few of the common env values include:
+
+* __window-development__: This is value when using Steal in dev mode in the browser.
+* __window-production__: This is the value set for production builds, built using [steal-tools].
+* __server-development__ / __server-production__: These are values set by [done-ssr](https://github.com/donejs/done-ssr) when loading a Steal application for server-side rendering purposes.
+* __electron-production__: Set when using the [steal-electron](https://github.com/stealjs/steal-electron) plugin.
+* __cordova-production__: Set when using the [steal-cordova](https://github.com/stealjs/steal-cordova) plugin.