Add a Key4hep based CI workflow

.github/workflows/key4hep.yml

@@ -0,0 +1,28 @@
+name: Key4hep build
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+  workflow_dispatch:
+  schedule:
+    - cron: 16 4 * * 1
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        build_type: ["release", "nightly"]
+        image: ["alma9"]
+        include:
+          - build_type: "nightly"
+            image: ubuntu24
+    steps:
+    - uses: actions/checkout@v5
+    - uses: key4hep/key4hep-actions/key4hep-build@main
+      with:
+        build_type: ${{ matrix.build_type }}
+        image: ${{ matrix.image }}