FileSystem: need support for Apps root directory (parent of /files)

## Feature Request

### Plugin

- FileSystem

### Description
I need access to the apps root directory. Actually the DATA-directory give access to '/data/user/0/app-id/**files**.
I need access to the parent directory of **files**: '/data/user/0/app-id/'. Because my sqlite database is stored under '/data/user/0/app-id/databases/sqlite.db'. And I would like to export this db.
The cordova-plugin-file uses the code 'context.getFilesDir().getParentFile()' to access this directory.

### Platform(s)

- Android

### Preferred Solution
The cordova-plugin-file uses the code 'context.getFilesDir().getParentFile()' to access this directory.
Add a new enum value 'DATA_ROOT' or change existing 'DATA' to 'DATA_FILES' and use 'DATA' for root access.

### Alternatives
-

### Additional Context
-