WIP: CI for demo building

.github/workflows/demo.yml

@@ -0,0 +1,29 @@
+name: Demo
+
+on: [push, pull_request]
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  build:
+    name: Build demo
+    runs-on: ubuntu-22.04
+    env:
+      DOCKERIZE_VERSION: v0.6.1
+    steps:
+      - uses: actions/checkout@v4
+      - run: |
+          podman build -t demo -f securedrop/dockerfiles/focal/python3/DemoDockerfile .
+      - run: |
+          # Install dockerize
+          wget https://github.com/jwilder/dockerize/releases/download/$DOCKERIZE_VERSION/dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz
+          tar -C /usr/local/bin -xzvf dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz
+          rm dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz
+      - run: |
+          # Start the container in the background
+          podman run -t -p 8080:8080 -p 8081:8081 --rm demo
+          # And wait for both ports to be up!
+          dockerize -wait http://127.0.0.1:8080 -timeout 30m
+          dockerize -wait http://127.0.0.1:8081 -timeout 30m