lnrpc: add maxFeeRatio to FundPsbtRequest

lnrpc/walletrpc/walletkit.proto

@@ -1417,6 +1417,9 @@ message FundPsbtRequest {
 
     // The strategy to use for selecting coins during funding the PSBT.
     lnrpc.CoinSelectionStrategy coin_selection_strategy = 10;
+
+    // The max fee to total output amount ratio that this psbt should adhere to.
+    double max_fee_ratio = 12;
 }
 message FundPsbtResponse {
     /*