add nix test case

.github/workflows/nix.yml

@@ -0,0 +1,32 @@
+---
+name: Test Nix
+on: [push, pull_request]
+jobs:
+  pfhub-nix-test:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./ro-crate-examples
+    steps:
+      - uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v20
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+          name: pfhub
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+          extraPullNames: nix-community
+      - run: echo "UID=${UID}" >> $GITHUB_ENV
+      - uses: actions/cache/restore@v3
+        with:
+          path: /run/user/${{ env.UID }}/http_cache.sqlite
+          key: ${{ runner.os}}-http_cache.sqlite
+      - run: nix develop --command bash -c "py.test --cov-fail-under=100"
+      - run: nix develop --command bash -c "black --check rocrate_cli"
+      - run: nix develop --command bash -c "pylint rocrate_cli"
+      - run: nix develop --command bash -c "flake8 rocrate_cli"
+      - run: nix develop --command bash -c "pfhub test"        
+      - uses: actions/cache/save@v3
+        if: always()
+        with:
+          path: /run/user/${{ env.UID }}/http_cache.sqlite
+          key: ${{ runner.os}}-http_cache.sqlite