Add nix flake

.gitignore

@@ -18,3 +18,6 @@
 # Ignore Vim temporary and swap files.
 *.sw?
 *~
+
+# Ignore nix build output
+result

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1697456312,
+        "narHash": "sha256-roiSnrqb5r+ehnKCauPLugoU8S36KgmWraHgRqVYndo=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "ca012a02bf8327be9e488546faecae5e05d7d749",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,27 @@
+{
+  description = "Twitch chat in the terminal.";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+  let
+    system = "x86_64-linux";
+    pkgs = nixpkgs.legacyPackages.${system};
+    manifest = (pkgs.lib.importTOML ./Cargo.toml).package;
+  in {
+    packages.${system}.default = pkgs.rustPlatform.buildRustPackage {
+      pname = manifest.name;
+      version = manifest.version;
+
+      buildInputs = [pkgs.openssl.dev];
+      nativeBuildInputs = [pkgs.pkg-config];
+
+      src = pkgs.lib.cleanSource ./.;
+      cargoLock.lockFile = ./Cargo.lock;
+    };
+
+    apps.${system}.default = {
+      type = "app";
+      program = "${self.packages.${system}.default}/bin/twt";
+    };
+  };
+}