Add Nix devshell build to CI

.github/workflows/ci.yml

@@ -51,6 +51,24 @@ jobs:
           nix -L build .#$NAME
           nix run .#$NAME -- domains
 
+  nix-build-devshell:
+    name: Nix build devshell
+    runs-on: macos-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v3
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v4
+
+      - name: Setup cache
+        uses: DeterminateSystems/magic-nix-cache-action@main
+
+      - name: Build and test
+        run: |
+          nix -L develop . --command echo "OK"
+
   stack-build:
     name: Stack build
     runs-on: macos-latest