Add basic GitHub workflow

.github/workflows/check.yml

@@ -0,0 +1,23 @@
+name: nix flake check
+
+on:
+  push:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        system: [ 'x86_64-linux', 'aarch64-linux' ]
+    steps:
+    - uses: actions/checkout@v4
+    - run: |
+        curl --proto '=https' --tlsv1.3 -sSf -L https://install.lix.systems/lix \
+        | sh -s -- install --no-confirm --enable-flakes --nix-build-user-count "$(nproc || sysctl -n hw.ncpu)" \
+        --extra-conf "
+        accept-flake-config = true
+        experimental-features = nix-command flakes pipe-operator
+        trusted-users = root $USER
+        "
+    - uses: DeterminateSystems/magic-nix-cache-action@v8
+    - run: nix --option allow-import-from-derivation true flake check