Update docs (#1019)

docs/styling-the-navigator.md

 {
   navigationBarColor: '#000000', // change the background color of the bottom native navigation bar. Android only
   navBarTextColor: '#000000', // change the text color of the title (remembered across pushes)
+  navBarTextFontFamily: 'font-name', // Changes the title font
+  navBarTitleTextCentered: true, // Android only. centers the title, default false.
   navBarBackgroundColor: '#f7f7f7', // change the background color of the nav bar (remembered across pushes)
   navBarButtonColor: '#007aff', // change the button colors of the nav bar (eg. the back button) (remembered across pushes)
   navBarHidden: false, // make the nav bar hidden
 }
 ```
 
-> Note: If you set any styles related to the Status Bar, make sure that in Xcode > project > Info.plist, the property `View controller-based status bar appearance` is set to `YES`.
+## Styling the StatusBar
+If you set any styles related to the Status Bar, make sure that in Xcode > project > Info.plist, the property `View controller-based status bar appearance` is set to `YES`.
+
+## Custom fonts
+If you'd like to use a custom font, you'll first have to your project.
+
+* Android - add the `.ttf` or `.otf` files to `src/main/assets/fonts/`
+
+* iOS - follow this [guide](https://medium.com/@dabit3/adding-custom-fonts-to-react-native-b266b41bff7f)
 
 All supported styles are defined [here](https://github.com/wix/react-native-controllers#styling-navigation). There's also an example project there showcasing all the different styles.