Revert "synth validation was moved to pre-deploy-check (#6)" (#11)

This reverts commit ac8a243.
Restore synth check

.github/workflows/check.yml

@@ -16,3 +16,19 @@ jobs:
         run: pip install -r requirements.txt -r requirements-dev.txt
       - name: Run unit tests
         run: python -m pytest tests/ -s -v
+  synth:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+      - name: Install dependencies
+        run: pip install -r requirements.txt -r requirements-dev.txt
+      - name: Generate cloudformation
+        uses: youyo/aws-cdk-github-actions@v2
+        env:
+          ENV: dev
+        with:
+          cdk_subcommand: 'synth'
+          actions_comment: false
+          debug_log: true
+          cdk_args: '--output ./cdk.out'