update docs/bottom-tab-navigator.md

Author: Jacek Grzybowski

docs/bottom-tab-navigator.md

@@ -20,6 +20,7 @@ The route configs object is a mapping from route name to a route config, which t
 ## BottomTabNavigatorConfig
 
 * `initialRouteName` - The routeName for the initial tab route when first loading.
+* `resetOnBlur` - Reset the state of any nested navigators when switching away from a screen. Defaults to `false`.
 * `order` - Array of routeNames which defines the order of the tabs.
 * `paths` - Provide a mapping of routeName to path config, which overrides the paths set in the routeConfigs.
 * `backBehavior` - Should the back button cause a tab switch to the initial tab? If yes, set to `initialRoute`, otherwise `none`. Defaults to `initialRoute` behavior.