kotlin double tab exit button

To create a double tap exit button in Kotlin, follow these steps:

1. Create a global variable to hold the last time the back button was pressed.
2. Override the onBackPressed() method and implement the double tap logic.
3. Check if the time difference between the current press and the last press is less than a certain threshold.
4. If the time difference is less than the threshold, exit the app. Otherwise, update the last press time and display a message.