ci: nix flake check

Signed-off-by: Christina Sørensen <christina@cafkafk.com>

.github/workflows/flake.yml

@@ -0,0 +1,17 @@
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  build:
+    name: Build Nix targets
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v3
+      - name: Check Nix flake inputs
+        uses: DeterminateSystems/flake-checker-action@v4 # This action
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v3
+      - name: Build default package
+        run: nix build