refactored nixos directory & updated README

nixos/virtualisation.nix

@@ -0,0 +1,44 @@
+{ pkgs, ... }:
+
+{
+  # Enable Containerd
+  # virtualisation.containerd.enable = true;
+
+  # Enable Docker
+  # virtualisation.docker.enable = true;
+  # virtualisation.docker.rootless = {
+  #   enable = true;
+  #   setSocketVariable = true;
+  # };
+  # users.extraGroups.docker.members = [ "xnm" ];
+
+  # Enable Podman
+  virtualisation = {
+    podman = {
+      enable = true;
+
+      # Create a `docker` alias for podman, to use it as a drop-in replacement
+      dockerCompat = true;
+
+      # Required for containers under podman-compose to be able to talk to each other.
+      defaultNetwork.settings.dns_enabled = true;
+    };
+  };
+
+  environment.systemPackages = with pkgs; [
+    # nerdctl
+
+    # firecracker
+    # firectl
+    # flintlock
+
+    distrobox
+    qemu
+
+    podman-compose
+    podman-tui
+
+    # lazydocker
+    # docker-credential-helpers
+  ];
+}