test: check Docker availability in runner

.forgejo/workflows/test-docker.yml

@@ -0,0 +1,19 @@
+name: Test Docker
+
+on:
+  push:
+    branches: [main, master]
+  workflow_dispatch:
+
+jobs:
+  docker-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Docker version
+        run: docker version
+      - name: Docker info
+        run: docker info
+      - name: Test docker login
+        run: echo "Docker is available, checking credentials..."
+      - name: Test build
+        run: docker run --rm hello-world