feat: add a nix package and devshell

flake.nix

@@ -0,0 +1,13 @@
+{
+  description = "sermo, an ircd written in rust";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    import-tree.url = "github:vic/import-tree";
+  };
+
+  outputs = inputs:
+    inputs.flake-parts.lib.mkFlake {inherit inputs;}
+    (inputs.import-tree ./packages/nix);
+}