Create Dart snippets and reference them

Co-Authored-By: ok300 <106775972+ok300@users.noreply.github.com>

snippets/dart_snippets/lib/receive_onchain.dart

@@ -0,0 +1,61 @@
+import 'package:breez_sdk/breez_sdk.dart';
+import 'package:breez_sdk/bridge_generated.dart';
+
+Future<SwapInfo> generateReceiveOnchainAddress() async {
+  // ANCHOR: generate-receive-onchain-address
+  ReceiveOnchainRequest req = const ReceiveOnchainRequest();
+  SwapInfo swapInfo = await BreezSDK().receiveOnchain(req: req);
+
+  // Send your funds to the below bitcoin address
+  final address = swapInfo.bitcoinAddress;
+  print(address);
+  return swapInfo;
+  // ANCHOR_END: generate-receive-onchain-address
+}
+
+Future<SwapInfo?> getInProgressSwap() async {
+  // ANCHOR: in-progress-swap
+  SwapInfo? swapInfo = await BreezSDK().inProgressSwap();
+  print(swapInfo);
+  // ANCHOR_END: in-progress-swap
+  return swapInfo;
+}
+
+Future<List<SwapInfo>> listRefundables() async {
+  // ANCHOR: list-refundables
+  List<SwapInfo> refundables = await BreezSDK().listRefundables();
+  for (var refundable in refundables) {
+    print(refundable.bitcoinAddress);
+  }
+  // ANCHOR_END: list-refundables
+  return refundables;
+}
+
+Future<RefundResponse> executeRefund({
+  required String swapAddress,
+  required String toAddress,
+  required int satPerVbyte,
+}) async {
+  // ANCHOR: execute-refund
+  RefundRequest req = RefundRequest(
+    swapAddress: swapAddress,
+    toAddress: toAddress,
+    satPerVbyte: satPerVbyte,
+  );
+  RefundResponse resp = await BreezSDK().refund(req: req);
+  print(resp.refundTxId);
+  // ANCHOR_END: execute-refund
+  return resp;
+}
+
+Future<OpenChannelFeeResponse> getChannelOpeningFees({
+  required int amountMsat,
+  int? expiry,
+}) async {
+  // ANCHOR: get-channel-opening-fees
+  OpenChannelFeeRequest req = OpenChannelFeeRequest(amountMsat: amountMsat, expiry: expiry);
+  OpenChannelFeeResponse resp = await BreezSDK().openChannelFee(req: req);
+  print(resp.feeMsat);
+  // ANCHOR_END: get-channel-opening-fees
+  return resp;
+}