build: add ci nix flake check action

Author: erooke

.github/workflows/check-flake.yml

@@ -0,0 +1,14 @@
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  lints:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - run: nix flake check