Add zizmor security scanner

Run zizmor on pushes to master and pull requests that modify workflow
files. Results are uploaded as SARIF to GitHub's security-events API for
code scanning integration.

Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

Author: stephenfin

.github/workflows/zizmor.yaml

@@ -0,0 +1,28 @@
+name: zizmor
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - '.github/**'
+  pull_request:
+    paths:
+      - '.github/**'
+
+permissions: {}
+
+jobs:
+  zizmor:
+    runs-on: ubuntu-latest
+    permissions:
+      security-events: write
+      contents: read
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+
+      - name: Run zizmor
+        uses: zizmorcore/zizmor-action@b1d7e1fb5de872772f31590499237e7cce841e8e # v0.5.3