Mention how to stop the node cleanly in the README

[fauns-baptism]

Overview

The base/node documentation explains how to start the node, but it doesn’t clearly mention the recommended way to stop it.
New users may not know whether they should use a specific command, send a signal, or just kill the process. This can cause confusion or improper shutdowns.

Proposed Solution

Add a short note to the README describing the recommended way to shut down the node and any signals it handles.