update Install.md

INSTALL.md

@@ -2,6 +2,52 @@
 
 We have packaged `swhkd-git`. `swhkd-bin` has been packaged separately by a user of swhkd.
 
+## NixOS
+
+For now flake users only.
+
+This repo contains a NixOS Module for swhkd service.
+To enable module add an input first and import to modules:
+```nix
+{
+  inputs = {
+    swhkd.url = "github:id3v1669/swhkd";
+  }
+
+  outputs = {nixpkgs, swhkd, ...} @ inputs: {
+    nixosConfigurations.HOSTNAME = nixpkgs.lib.nixosSystem {
+      specialArgs = { inherit inputs; };
+      modules = [
+        ./configuration.nix
+        swhkd.nixosModules.default
+      ];
+    };
+  } 
+}
+```
+After importing you should be able to use it in your configuration.nix file:
+```nix
+{ inputs
+, ...
+}:
+{
+  services.swhkd = {
+    enable = true;
+    package = inputs.swhkd.packages.${system}.default;
+    cooldown = 300;
+    settings = ''
+super + return
+  alacritty
+    '';
+  };
+}
+```
+* Do not forget to start/add to autostart swhkd of your system after login.
+* Replace HOSTNAME with your oun
+
+ps. this module will be updated after refactor of security model, but 
+it is already good enough to use
+
 # Building:
 
 `swhkd` and `swhks` install to `/usr/local/bin/` by default. You can change this behaviour by editing the [Makefile](../Makefile) variable, `DESTDIR`, which acts as a prefix for all installed files. You can also specify it in the make command line, e.g. to install everything in `subdir`: `make DESTDIR="subdir" install`.