chore: add README

README.md

@@ -0,0 +1,46 @@
+# Nix Gitlab CI
+
+Flake module which allows generating a `.gitlab-ci.yml` from Nix.
+This allows easily using any Nix package in CI.
+Also makes it possible to split CI parts in a separate module 
+which can be imported in multiple projects.
+
+
+## Usage
+```nix
+# flake.nix
+{
+  ...
+  inputs.nix-gitlab-ci.url = "gitlab:TECHNOFAB/nix-gitlab-ci";
+  
+  outputs = {...}: flake-parts.lib.mkFlake {...} {
+    imports = [
+      inputs.nix-gitlab-ci.flakeModule
+    ];
+    ...
+    
+    perSystem = {...}: {
+      ci = {
+        stages = ["test"];
+        jobs = {
+          "test" = {
+            stage = "test";
+            deps = [pkgs.unixtools.ping];
+            script = [
+              "ping -c 5 8.8.8.8"
+            ];
+          };
+        };
+      };
+      ...
+    }
+  }
+}
+```
+```yaml
+# .gitlab-ci.yml
+include:
+  - project: TECHNOFAB/nix-gitlab-ci
+    ref: main
+    file: gitlab-ci.yml
+```