Allow to fail early (pre-commit time) for jinja error, rather than waiting until executing the playbook and the invalid template. I could not find a simple jinja pre-commit hook in the wild.
* add pre-commit hook configuration * add tmp.md to .gitignore * describe the use of pre-commit hook in CONTRIBUTING.md * fix docs/integration.md errors identified by markdownlint * fix docs/<file>.md errors identified by markdownlint * docs/azure-csi.md * docs/azure.md * docs/bootstrap-os.md * docs/calico.md * docs/debian.md * docs/fcos.md * docs/vagrant.md * docs/gcp-lb.md * docs/kubernetes-apps/registry.md * docs/setting-up-your-first-cluster.md * docs/vagrant.md * docs/vars.md * fix contrib/<file>.md errors identified by markdownlint