docs(plugins): finish documenting the available options for the HotModuleReplacementPlugin

Author: skipjack

content/plugins/hot-module-replacement-plugin.md

@@ -20,7 +20,7 @@ Enabling HMR is easy and in most cases no options are necessary.
 
 ``` javascript
 new webpack.HotModuleReplacementPlugin({
-    // Options...
+  // Options...
 })
 ```
 
@@ -29,5 +29,7 @@ new webpack.HotModuleReplacementPlugin({
 
 The following options are accepted:
 
-- `multiStep` (?): TODO...
-- `fullBuildTimeout` (number): TODO...
+- `multiStep` (boolean): If `true`, the plugin will build in two steps -- first compiling the hot update chunks, and then the remaining normal assets.
+- `fullBuildTimeout` (number): The delay between the two steps when `multiStep` is enabled.
+
+W> These options are experimental and may be deprecated. As mentioned above, they are typically not necessary and including a `new webpack.HotModuleReplacementPlugin()` is enough.