task: run ansible in syntax check mode

Part of #1631

[skip ci]

Author: php-coder

.github/workflows/provision-by-ansible.yml

@@ -32,3 +32,7 @@ jobs:
         # The command pip3 install --user ansible==2.10.17 doesn't work as we have an old version
         # See https://docs.ansible.com/ansible/2.10/installation_guide/intro_installation.html#installing-devel-from-github-with-pip
         run: python3 -m pip install --user https://github.com/ansible/ansible/archive/refs/tags/v2.10.17.tar.gz
+
+      - name: Run ansible in syntax check mode
+        run: ansible-playbook provisioning/prod.yml -i provisioning/prod.inventory --syntax-check
+        working-directory: infra/vagrant