Add unit test workflow based on salt-test

.github/workflows/unit-opensuse.yml

@@ -0,0 +1,25 @@
+name: Unit tests
+
+on:
+  push:
+    branches: [openSUSE/release/3006.0]
+  pull_request:
+    branches: [openSUSE/release/3006.0]
+  workflow_dispatch:
+
+jobs:
+  unit-tests:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout Salt
+        uses: actions/checkout@v4
+      - name: Run unit tests
+        container:
+          image: registry.opensuse.orgsystemsmanagement/saltstack/products/testing/containers/leap15.5/containers/salt-testsuite-github:leap15.5
+          volumes:
+            - salt:/code
+
+        run: |
+          salt-test --skiplist https://raw.githubusercontent.com/openSUSE/salt-test-skiplist/main/skipped_tests.toml \
+            --directory /code --package-flavor classic unit