github-ci: add

.github/workflows/nix.yml

@@ -0,0 +1,25 @@
+---
+
+on:
+  pull_request:
+  push:
+    branches: [main, master]
+
+jobs:
+  build:
+    name: Build Nix targets
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Git checkout
+        uses: actions/checkout@v3
+      - name: Install Nix
+        uses: cachix/install-nix-action@v22
+      - name: Check Nix flake inputs
+        uses: DeterminateSystems/flake-checker-action@v5
+        with:
+          ignore-missing-flake-lock: false
+          fail-mode: true
+      - name: Check Nix flake
+        run: nix flake check
+      # - name: Build Nix packages
+      #   run: nix build

README.md

@@ -1,4 +1,4 @@
-# nixos-config [![built with nix](https://builtwithnix.org/badge.svg)](https://builtwithnix.org)
+# nixos-config [![built with nix](https://builtwithnix.org/badge.svg)](https://builtwithnix.org)![CI](https://github.com/Stunkymonkey/nixos/actions/workflows/nix.yml/badge.svg)
 
 This repository holds my NixOS configuration.
 It is fully reproducible, flakes based, and position-independent, ...