rpc: add "ischange: true" in wallet gettransaction decoded tx output

src/rpc/rawtransaction.cpp

@@ -118,6 +118,7 @@ static std::vector<RPCResult> DecodeTxDoc(const std::string& txid_field_doc)
                 {RPCResult::Type::STR_AMOUNT, "value", "The value in " + CURRENCY_UNIT},
                 {RPCResult::Type::NUM, "n", "index"},
                 {RPCResult::Type::OBJ, "scriptPubKey", "", ScriptPubKeyDoc()},
+                {RPCResult::Type::BOOL, "ischange", /*optional=*/true, "Output script is change (only if wallet transaction and true for selected rpcwallet)"},
             }},
         }},
     };