rpc: add cli example for walletcreatefundedpsbt RPC

The only example present earlier was one that creates an OP_RETURN output. This
lack of examples has discouraged me earlier to use this RPC. Adding an example
that creates PSBT sending bitcoin to address, a scenario that is much more common.

Author: rkrux

src/wallet/rpc/spend.cpp

@@ -1729,8 +1729,10 @@ RPCHelpMan walletcreatefundedpsbt()
                     }
                                 },
                                 RPCExamples{
-                            "\nCreate a transaction with no inputs\n"
-                            + HelpExampleCli("walletcreatefundedpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+                            "\nCreate a PSBT with automatically picked inputs that sends 0.5 BTC to an address and has a fee rate of 2 sat/vB:\n"
+                            + HelpExampleCli("walletcreatefundedpsbt", "\"[]\" \"[{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.5}]\" 0 \"{\\\"add_inputs\\\":true,\\\"fee_rate\\\":2}\"")
+                            + "\nCreate the same PSBT as the above one instead using named arguments:\n"
+                            + HelpExampleCli("-named walletcreatefundedpsbt", "outputs=\"[{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.5}]\" add_inputs=true fee_rate=2")
                                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {