chore(docs v7): Added screenshots for headerBackTitle

Author: stanleyoos

static/assets/7.x/native-stack/headerBackTitle/headerBackTitle.jpeg

@@ -182,6 +182,8 @@ Title string used by the back button on iOS. Defaults to the previous scene's ti
 
 Only supported on iOS.
 
+<img src="/assets/7.x/native-stack/headerBackTitle/headerBackTitle.jpeg" height="700" alt="Header back title" />
+
 #### `headerBackTitleVisible`
 
 Whether the back button title should be visible or not.
@@ -197,6 +199,8 @@ Style object for header back title. Supported properties:
 
 Only supported on iOS.
 
+<img src="/assets/7.x/native-stack/headerBackTitleStyle/headerBackTitleStyle.png" width="500" alt="Header back title style" />
+
 #### `headerBackImageSource`
 
 Image to display in the header as the icon in the back button. Defaults to back icon image for the platform