Tweak README

Dependencies

• [2] 52F4Q6CJ Update README
• [3] 7AUC4NKI Initial commit
• [4] SNMYL7H6 Update README

Change contents

• replacement in README.md at line 3
  [3.3668]→[3.3668:3728](∅→∅)
  − Scripts to (interactively) demonstrate capabilities of Nix.
  [3.3668]

  [2.173]
  + Scripts to (interactively) demonstrate capabilities of [Nix](https://nixos.org/).
• replacement in README.md at line 7
  [2.191]→[2.191:337](∅→∅)
  − [Nix](https://nixos.org/download.html) with [flakes enabled](https://github.com/mschwaig/howto-install-nix-with-flake-support) must be available.
  [2.191]

  [2.338]
  + Nix with [flakes enabled](https://github.com/mschwaig/howto-install-nix-with-flake-support) must be available.