docs: Add documentation for health check API endpoint

docs/config.md

@@ -1067,6 +1067,16 @@ and [here](https://easyengine.io/tutorials/nginx/block-wp-login-php-bruteforce-a
     maxretry = 10
     ```
 
+## Health checks
+A preliminary health check API endpoint is exposed at `"/v1/health"`. The endpoint returns a `json` response in the format shown below.
+If a non-200 HTTP status code is returned or if the returned `health` field is `false` the ntfy service should be considered as unhealthy.
+
+```json
+{"health":true}
+```
+
+See [Installalation/Docker](install.md#docker) for an example of how this could be used in a `docker-compose` environment.
+
 ## Logging & debugging
 By default, ntfy logs to the console (stderr), with an `info` log level, and in a human-readable text format.