feat(permissionsandroid): add voicemail permissions

Author: gedeagas

docs/permissionsandroid.md

@@ -185,6 +185,8 @@ Available as constants under `PermissionsAndroid.PERMISSIONS`:
 - `READ_MEDIA_AUDIO`: 'android.permission.READ_MEDIA_AUDIO'
 - `POST_NOTIFICATION`: 'android.permission.POST_NOTIFICATIONS'
 - `NEARBY_WIFI_DEVICES`: 'android.permission.NEARBY_WIFI_DEVICES'
+- `READ_VOICEMAIL`: 'com.android.voicemail.permission.READ_VOICEMAIL',
+- `WRITE_VOICEMAIL`: 'com.android.voicemail.permission.WRITE_VOICEMAIL',
 
 ### Result strings for requesting permissions