docs: keepAlive and keepAliveInitialDelayMillis (#3609)

Co-authored-by: Corey Van Woert <corey.vanwoert@helloalfred.com>

Author: charmander

docs/pages/apis/client.mdx

@@ -23,7 +23,9 @@ type Config = {
   lock_timeout?: number, // number of milliseconds a query is allowed to be en lock state before it's cancelled due to lock timeout
   application_name?: string, // The name of the application that created this Client instance
   connectionTimeoutMillis?: number, // number of milliseconds to wait for connection, default is no timeout
-  keepAliveInitialDelayMillis?: number, // set the initial delay before the first keepalive probe is sent on an idle socket
+  keepAlive?: boolean, // if true, enable keepalive on the `net.Socket`
+  keepAliveInitialDelayMillis?: number, // number of milliseconds between last data packet received and first keepalive probe, default is 0 (keep existing value);
+                                        // no effect unless `keepAlive` is true
   idle_in_transaction_session_timeout?: number, // number of milliseconds before terminating any session with an open idle transaction, default is no timeout
   client_encoding?: string, // specifies the character set encoding that the database uses for sending data to the client
   fallback_application_name?: string, // provide an application name to use if application_name is not set