Use nix run for pygments

Dependencies

• [2] P34QQPLU Pin shellcheck / pygmentize
• [3] VMUKZQZR Work on 02-nix-build
• [4] PO6SMI7O Reduce dependency of libdemo on Nix
• [5] 55PCHITP Clean up libdemo
• [*] 7AUC4NKI Initial commit

Change contents

• replacement in libdemo/libdemo.sh at line 212
  [3.120]→[2.4:191](∅→∅)
  − COLORTERM="" TERM="" "$(nix build github:nixos/nixpkgs/008ce261a7e3c532e792cb8e39482f2cc1b192f5#python3Packages.pygments --no-link --print-out-paths)/bin/pygmentize" "$@"
  [3.120]

  [3.253]
  + COLORTERM="" TERM="" nix run github:sfrijters/nixpkgs/pygments-mainprogram#python3Packages.pygments "$@"