build: add docker build step to test workflow

.forgejo/workflows/test.yml

@@ -8,6 +8,15 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Install Docker CLI
+        run: |
+          curl -fsSL https://get.docker.com -o get-docker.sh
+          sh get-docker.sh
+          sudo apt-get update && sudo apt-get upgrade -y
+
+      - name: docker build
+        run: docker build .
+
       - name: Test
         uses: https://git.kemitix.net/kemitix/rust@next
         with: