Add CI step for nix build and flake check

Author: dbrgn

.github/workflows/ci.yml

@@ -128,3 +128,15 @@ jobs:
           tags: |
             ghcr.io/dbrgn/xc-bot:${{ steps.version.outputs.branch }}
             ghcr.io/dbrgn/xc-bot:${{ steps.version.outputs.version }}
+
+  nix-build:
+    name: Build nix package
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - uses: cachix/install-nix-action@v31
+        with:
+          nix_path: nixpkgs=channel:nixos-25.05
+          github_access_token: ${{ secrets.GITHUB_TOKEN }}
+      - run: nix-build
+      - run: nix flake check

README.md

@@ -55,6 +55,10 @@ You'll probably want to mount both files into the container.
 Note: This container runs as default user by default. If you use podman, you
 can run the container as non-root.
 
+## Nix MOdule
+
+This repository also includes a Nix package and NixOS module.
+
 ## License
 
 Licensed under the AGPL version 3 or later. See `LICENSE.md` file.