Document runtime.shutdown_timeout param (#966)

* Document runtime.shutdown_timeout param

* Update runtime.md

Author: sgrebnov

website/docs/reference/spicepod/runtime.md

@@ -37,6 +37,15 @@ runtime:
 
 Use `sql` for the lowest latency with identical queries that do not include dynamic functions. Use `plan` for greater flexibility.
 
+## `runtime.shutdown_timeout`
+
+Controls how long Spice waits for connections to be gracefully drained and for components to shut down cleanly during runtime termination. Defaults to 30 seconds. 
+
+```yaml
+runtime:
+  shutdown_timeout: 1m
+```
+
 ## `runtime.tls`
 
 The TLS section specifies the configuration for enabling Transport Layer Security (TLS) for all endpoints exposed by the runtime. [Learn more about enabling TLS](/docs/api/tls/index.md).