Add sourceMap=inline docs

Author: ai

README.md

@@ -75,6 +75,17 @@ If there is the need, this will let you access to webpack loaders API.
 
 [webpack loader-context]: http://webpack.github.io/docs/loaders.html#loader-context
 
+Loader accepts `sourceMap=inline` to put source maps
+into CSS annotation comment:
+
+```js
+module.exports = {
+    module: {
+        loader: "style-loader!css-loader!postcss-loader?sourceMap=inline"
+    }
+}
+```
+
 ## Plugins Packs
 
 If you want to process different styles by different PostCSS plugins you can