add a new workflow to use nix and replace github actions setup with p…

…ython

.github/workflows/build.yaml

@@ -0,0 +1,20 @@
+name: Build
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-22.04
+    permissions:
+      id-token: "write"
+      contents: "read"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - uses: DeterminateSystems/flake-checker-action@main
+      - name: Run tests
+        run: pytest
+        shell: nix develop --command bash -e {0}