Update readme

- add usage, design idea
- update other projects

README.md

@@ -1,11 +1,32 @@
-# nixos-modukles
+# nixos-modules
 
-Opinionated shared nixos configurations.
+Opinionated shared NixOS configurations.
 
-# Usage
+## Usage
 
-TODO
+Add or merge the following settings to your `flake.nix`:
 
-# Similar projects
+```nix
+{
+  inputs = {
+    nixos-modules.url = "github:SuperSandro2000/nixos-modules";
+  };
 
-- https://github.com/numtide/srvos
+  outputs = { nixos-modules }: {
+    nixosConfigurations.HOSTNAME = {
+      modules = [
+       nixos-modules.nixosModule
+    ];
+  };
+}
+```
+
+## Design
+
+* Modules should never change the configuration without setting an option
+* Unless the global overwrite ``opinionatedDefaults = true`` is set which activates most settings.
+
+## Similar projects
+
+* https://github.com/numtide/srvos
+* https://gitea.c3d2.de/C3D2/nix-user-module