nix: make the repository a flake

Now you can build the bot using `nix build .#telegram`
The discord bot is still a TODO

Author: akshatagarwl

flake.lock

@@ -0,0 +1,33 @@
+{
+  description = "";
+
+  inputs = {
+    utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, utils }:
+    utils.lib.eachDefaultSystem (system: let
+      pkgs = nixpkgs.legacyPackages."${system}";
+      lib = pkgs.lib;
+    in rec {
+      # `nix build`
+      packages.telegram = pkgs.buildGoModule rec {
+        name = "telegram-bot";
+        src = ./telegram-bot;
+
+        vendorSha256 = "sha256-NBY2T0Jj5f9XMoc0hleituKHFf+9AFq056a/EpCsuXo=";
+      };
+      defaultPackage = packages.telegram;
+
+      # `nix run`
+      apps.telegram = utils.lib.mkApp {
+        drv = packages.telegram;
+      };
+      defaultApp = apps.telegram;
+
+      # `nix develop`
+      devShell = pkgs.mkShell {
+        nativeBuildInputs = with pkgs; [ go ];
+      };
+    });
+}