bento: use flake-utils to support all systems

rework README

bento: recreate the state file for every rebuild

lock: bump nixpkgs version

flake: remove version

bento: add command diff

bento: add auto reboot mode

bento: add BENTO_DIR variable to automatically use the right place fo…

…r bento commands

bento: add a new option to update flakes recursively

bump flake version