docs: add maxLifetimeSeconds to Pool docs (#3484)

Wording taken from #3298 (comment)

Author: birjj

docs/pages/apis/pool.mdx

@@ -50,6 +50,12 @@ type Config = {
   // to the postgres server.  This can be handy in scripts & tests
   // where you don't want to wait for your clients to go idle before your process exits.
   allowExitOnIdle?: boolean
+
+  // Sets a max overall life for the connection.
+  // A value of 60 would evict connections that have been around for over 60 seconds,
+  // regardless of whether they are idle. It's useful to force rotation of connection pools through
+  // middleware so that you can rotate the underlying servers. The default is disabled (value of zero)
+  maxLifetimeSeconds?: number
 }
 ```
 
@@ -64,6 +70,7 @@ const pool = new Pool({
   max: 20,
   idleTimeoutMillis: 30000,
   connectionTimeoutMillis: 2000,
+  maxLifetimeSeconds: 60
 })
 ```