Add SMS Permission to Android App

I have the source code for an Android application and need a developer to integrate the default SMS permission into the app.

Key Requirements:
- Modify the app to request default SMS permissions at launch.
- Ensure no other permissions are affected.
- Maintain current app functionality and performance.

Ideal Skills:
- Proficient in Android app development.
- Experienced in modifying app permissions.
- Able to work with existing source code.

Please note, the application currently does not use any permissions. Your task will solely be to implement the SMS permission.