ci: add trivy scan

.github/workflows/trivy.yaml

@@ -0,0 +1,28 @@
+name: Trivy Scan
+
+on:
+  schedule:
+    - cron: "45 17 * * *" # need to use UTC time here
+  workflow_dispatch:
+
+
+jobs:
+  trivy_scan:
+    name: Trivy Scan
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Run Trivy vulnerability scanner
+        uses: aquasecurity/trivy-action@master
+        with:
+          image-ref: 'docker.io/virtomize/mail2most:latest'
+          format: 'sarif'
+          output: 'trivy-results.sarif'
+
+      - name: Upload Trivy scan results to GitHub Security tab
+        uses: github/codeql-action/upload-sarif@v2
+        if: always()
+        with:
+          sarif_file: 'trivy-results.sarif'