Added a flake for build and packaging on Nix/NixOS.

[deephack1982]

Created a simple flake which can build and install sidecar on Nix/NixOS environments just in case you want that. To locally build and test simply run

nix build

To add to your NixOS system you can add an input and include the default package like this.

inputs = {
    sidecar.url = "github:deephack1982/sidecar";

## more inputs
};

environment.systemPackages = with pkgs; [
  inputs.sidecar.packages.${pkgs.stdenv.hostPlatform.system}.default
]

[deephack1982]

Okay had to patch this up a bit as I included the wrong td :-D

NixOS snippet is now this.

inputs = {
    sidecar.url = "github:deephack1982/sidecar";

## more inputs
};

environment.systemPackages = with pkgs; [
  inputs.sidecar.packages.${pkgs.stdenv.hostPlatform.system}.sidecar
  inputs.sidecar.packages.${pkgs.stdenv.hostPlatform.system}.td
]