📚 Add note on the correct package name required to mount on startup

[Ambro17]

I've spent a few hours navigating goofy's issues and getting 2021-06-16T17:11:03.392028+00:00 ip-10-10-73-45 kernel: [ 9.551179] fuse: Unknown parameter '--file-mode when following the README instructions to mount on startup.

The suggested package fuse-utils was not found on Ubuntu 20.04.2 LTS mirros, but installing fuse with sudo apt install fuse worked and the bucket is now mounted on startup.

Let me know if you want the message rephrased clarifying the ubuntu version

Thank you for your awesome work maintaining the lib!

[Ambro17]

👋