ci: editorconfig: use nix-shell instead of nix-env

        # nixpkgs commit is pinned so that it doesn't break

        # editorconfig-checker 2.4.0

        nix_path: nixpkgs=https://github.com/NixOS/nixpkgs/archive/c473cc8714710179df205b153f4e9fa007107ff9.tar.gz

    - name: install editorconfig-checker

      run: nix-env -iA editorconfig-checker -f '<nixpkgs>'

    - name: Checking EditorConfig

      run: |

        cat "$HOME/changed_files" | xargs -r editorconfig-checker -disable-indent-size

        cat "$HOME/changed_files" | nix-shell -p editorconfig-checker --run 'xargs -r editorconfig-checker -disable-indent-size'

    - if: ${{ failure() }}

      run: |

        echo "::error :: Hey! It looks like your changes don't follow our editorconfig settings. Read https://editorconfig.org/#download to configure your editor so you never see this error again."