chore: Native Stack doc's - headerBackButtonMenuEnabled (react-navigation#1352)

* chore: Created new assets folder, added video for 'headerBackButtonMenuEnabled' option

* chore(docs v7): Added screenshots for headerBackTitle

* chore: moved all files to native-stack folder

* chore(docs): Updated images for header title

* chore(docs): Added code example for headerBackTitleStyle

* [autofix.ci] apply automated fixes

* chore(docs): Deleted unused line

* chore(docs): Updated code example

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: stanleyoos

static/assets/7.x/native-stack/headerBackButtonMenuEnabled.png

@@ -166,6 +166,8 @@ Requires `react-native-screens` version >=3.3.0.
 
 Only supported on iOS.
 
+<img src="/assets/7.x/native-stack/headerBackButtonMenuEnabled.png" width="500" alt="Header back button menu enabled" />
+
 #### `headerBackVisible`
 
 Whether the back button is visible in the header. You can use it to show a back button alongside `headerLeft` if you have specified it.
@@ -178,6 +180,8 @@ 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.jpeg" width="500" alt="Header back title" />
+
 #### `headerBackTitleVisible`
 
 Whether the back button title should be visible or not.
@@ -193,6 +197,17 @@ Style object for header back title. Supported properties:
 
 Only supported on iOS.
 
+<img src="/assets/7.x/native-stack/headerBackTitleStyle.png" width="500" alt="Header back title style" />
+
+Example:
+
+```js
+  headerBackTitleStyle: {
+      fontSize: 14,
+      fontFamily: 'Georgia',
+  },
+```
+
 #### `headerBackImageSource`
 
 Image to display in the header as the icon in the back button. Defaults to back icon image for the platform