docs: add comment about selecting payment network in quickstart

Author: cryptobench

examples/docs-examples/quickstarts/quickstart/requestor.mjs

@@ -26,6 +26,10 @@ const order = {
       level: "info",
     }),
     api: { key: "try_golem" },
+    // Optional: select payment network.
+    // Testnets:  holesky (default), sepolia, rinkeby, amoy
+    // Mainnets:  mainnet, polygon
+    // payment: { network: "holesky" },
   });
 
   try {