Get Started Page is missing copy folder location

[nirvn]

Originally filed by @arc12 at https://github.com/opengisch/QField/issues/4157

This page: https://docs.qfield.org/get-started/tutorials/get-started-qfs/ does not provide the location to which the package folder should be copied to for Android users. This would be very helpful for people getting started! I suggest locations for both "internal" and SD storage should be provided.