This function will set up a custom ALLEGRO_FS_INTERFACE(3) which allows working
within the APK filesystem. The filesystem root is your assets directory and
there is read-only access to all files within.
Note: Some things like querying file size or attributes are
not supported by this. You can always use the PhysFS addon to open the APK
file (it is just a regular .zip file) and get more complete information.