Add github CI

.github/workflows/ci.yaml

@@ -0,0 +1,22 @@
+name: "CI"
+on:
+  # Run only when pushing to master branch, and making PRs
+  push:
+    branches:
+      - master
+  pull_request:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: cachix/install-nix-action@v13
+        with:
+          install_url: https://nixos-nix-install-tests.cachix.org/serve/i6laym9jw3wg9mw6ncyrk6gjx4l34vvx/install
+          install_options: "--tarball-url-prefix https://nixos-nix-install-tests.cachix.org/serve"
+          extra_nix_config: |
+            experimental-features = nix-command flakes
+      - name: Build
+        id: build
+        run: |
+          nix build -j auto