Add trivy scan

.github/workflows/trivy.yml

@@ -0,0 +1,23 @@
+name: build
+on:
+  push:
+    branches:
+      - master
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Build image
+        run: docker build -t geoserver-docker.osgeo.org/geoserver:${{ github.sha }} .
+      - name: Run trivy
+        uses: aquasecurity/trivy-action@master
+        with:
+          image-ref: 'geoserver-docker.osgeo.org/geoserver:${{ github.sha }}'
+          format: 'table'
+          exit-code: '1'
+          ignore-unfixed: true
+          vuln-type: 'os,library'
+          severity: 'CRITICAL,HIGH'