Create files as root into /keybase folder

I'm trying to backup some system files of my Linux into my private keybase folder, but in order to do so I have to run the `cp` command as root, since only root has read permissions to some system files. I know FUSE mounting has the `allow_root` and `allow_other` flags to allow root user to access the mount point, but I can't find a way of passing it when using keybase. Note that I'm not running keybase as root, I'm running it as my regular user, I just want root to also have access to the /keybase/private folder so I can save my system backups in there.

Start by locating the Linux FUSE mount setup and how Keybase handles mount options; the issue specifically calls out allow_root and allow_other. Done means a mount created by a regular user permits root to read and write the /keybase/private folder for system backups without running Keybase as root.

Written by the indexing model from the issue text.