Reduce dependency of libdemo on Nix

Dependencies

• [2] VMUKZQZR Work on 02-nix-build
• [3] M5U5PAX7 Add wrapper script, improve libdemo
• [4] VXZ5QMIE Fix CI
• [*] 7AUC4NKI Initial commit

Change contents

• replacement in bash/libdemo.sh at line 192
  [2.2387]→[2.2387:2584](∅→∅)
  − # Hack around missing mainProgram attribute in pygments

  − COLORTERM="" TERM="" "$(nix build nixpkgs#python3Packages.pygments --no-link --print-out-paths)/bin/pygmentize" "$@"
  [2.2387]

  [2.2584]
  + if type nix >/dev/null; then

  + # Hack around missing mainProgram attribute in pygments

  + COLORTERM="" TERM="" "$(nix build nixpkgs#python3Packages.pygments --no-link --print-out-paths)/bin/pygmentize" "$@"

  + elif type pygmentize >/dev/null; then

  + pygmentize "$@"

  + else

  + echo "pygmentize command not found"

  + return 1

  + fi