RN: Add FeedbackWidget imagePicker prop example (#14012)

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Adds FeedbackWidget imagePicker prop example

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Author: antonis

docs/platforms/react-native/user-feedback/configuration/index.mdx

@@ -226,6 +226,14 @@ Sentry.init({
 });
 ```
 
+The `imagePicker` integration is used when launching the feedback widget with the `showFeedbackWidget` or the `FeedbackButton`. In order to use it with a custom `FeedbackWidget` component, you need to pass the `imagePicker` prop to the component as shown below:
+
+```javascript
+<FeedbackWidget
+  imagePicker={ImagePicker}
+/>
+```
+
 ### Implementing the `onAddScreenshot` Callback
 
 If the above libraries do not cover your use case you can manually integrate screenshots by implementing the `onAddScreenshot` callback. The callback receives the `uri` of the image like in the example below.