Add CI runs of demo checks.

.github/workflows/ci.yml

@@ -0,0 +1,35 @@
+name: Continuous Integration
+
+on:
+  push:
+    branches:
+      - "trunk"
+    tags:
+      - "*"
+    paths-ignore:
+      - "**.md"
+  pull_request:
+    branches:
+      - "trunk"
+    paths-ignore:
+      - "**.md"
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Statcheck test
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: true
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install make chocolate-doom python3 python3-yaml
+
+      - name: Run checks
+        run: |
+          make check