Bubblewrapped services: sandbox at tip

File services/sandbox from the latest check-in

#!/bin/bash

# Add support for nix-shell if available
if [[ -e "shell.nix" && $(which nix-shell) ]]; then
  echo Loading Nix packages
  nix-shell --run "$HOME/services/_sandbox $*"
elif [[ -e "packages.nix" && $(which nix-shell) ]]; then
  echo Loading Nix packages
  nix-shell -p $(xargs -a packages.nix echo) --run "$HOME/services/_sandbox $*"
else
  $HOME/services/_sandbox $*
fi