Update top-level-api.md (Added forgotten styles) (#1600)

* Update top-level-api.md (Added forgotten styles)

Added forgotten drawer style props.

* Added iOS only words to style objects

docs/top-level-api.md

       screen: 'example.SecondSideMenu', // unique ID registered with Navigation.registerScreen
       passProps: {} // simple serializable object that will pass as props to all top screens (optional)
     },
+    style: { // ( iOS only )
+      drawerShadow: true, // optional, add this if you want a side menu drawer shadow
+      contentOverlayColor: 'rgba(0,0,0,0.25)', // optional, add this if you want a overlay color when drawer is open
+      leftDrawerWidth: 50 // optional, add this if you want a define left drawer width (50=percent)
+      rightDrawerWidth: 50 // optional, add this if you want a define right drawer width (50=percent)
+    },
     disableOpenGesture: false // optional, can the drawer be opened with a swipe instead of button
   },
   passProps: {}, // simple serializable object that will pass as props to all top screens (optional)
       screen: 'example.SecondSideMenu', // unique ID registered with Navigation.registerScreen
       passProps: {} // simple serializable object that will pass as props to all top screens (optional)
     },
+    style: { // ( iOS only )
+      drawerShadow: true, // optional, add this if you want a side menu drawer shadow
+      contentOverlayColor: 'rgba(0,0,0,0.25)', // optional, add this if you want a overlay color when drawer is open
+      leftDrawerWidth: 50 // optional, add this if you want a define left drawer width (50=percent)
+      rightDrawerWidth: 50 // optional, add this if you want a define right drawer width (50=percent)
+    },
     disableOpenGesture: false // optional, can the drawer be opened with a swipe instead of button
   },
   passProps: {}, // simple serializable object that will pass as props to all top screens (optional)