Add installation via docker compose (MVP 1)

- Add markdown tabs blocks
- Fix [Issue 604](https://github.com/chatmail/relay/issues/604)
- Add `--skip-dns-check` argument to `cmdeploy run` command
- Add `--force` argument to `cmdeploy init` command
- Add startup for `fcgiwrap.service`
- Add extended check when installing `unbound.service`
- Add configuration parameters (`is_development_instance`, `use_foreign_cert_manager`, `acme_email`, `change_kernel_settings`, `fs_inotify_max_user_instances_and_watchers`)

docker/files/setup_chatmail.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=Run container setup commands
+After=multi-user.target
+ConditionPathExists=/setup_chatmail_docker.sh
+
+[Service]
+Type=oneshot
+ExecStart=/bin/bash /setup_chatmail_docker.sh
+RemainAfterExit=true
+WorkingDirectory=/opt/chatmail
+PassEnvironment=<envs_list>
+
+[Install]
+WantedBy=multi-user.target