Mention security notes in widget toolkit server

Signed-off-by: Michael Weimann <[email protected]>

README.md

@@ -154,7 +154,9 @@ Yon can run the widget using Docker:
 docker run --rm -e REACT_APP_HOME_SERVER_URL=https://matrix-client.matrix.org -p 8080:8080 ghcr.io/nordeck/matrix-neoboard-widget:latest
 ```
 
-Our docker image supports customizing the nginx config by supplying additional config files.
+Be sure, that you also read the security notes in the base image [@matrix-widget-toolkit/widget-server](https://github.com/nordeck/matrix-widget-toolkit/tree/main/containers/widget-server) docs.
+
+The image supports customizing the nginx config by supplying additional config files.
 For example, this allows running the image in an IPv4-only environment, as demonstrated at <https://github.com/nordeck/matrix-widget-toolkit/tree/main/containers/widget-server#custom-listen-directive>
 
 We also provide a [HELM chart](./charts/).