Add examples for adding extra TLVs to a spontaneous payment

snippets/react-native/send_spontaneous_payment.ts

@@ -1,4 +1,7 @@
-import { sendSpontaneousPayment } from '@breeztech/react-native-breez-sdk'
+import {
+  sendSpontaneousPayment,
+  type TlvEntry
+} from '@breeztech/react-native-breez-sdk'
 
 const exampleSendSpontaneousPayment = async () => {
   // ANCHOR: send-spontaneous-payment
@@ -10,3 +13,26 @@ const exampleSendSpontaneousPayment = async () => {
   })
   // ANCHOR_END: send-spontaneous-payment
 }
+
+const stringToBytes = (str: string): number[] => {
+  const bytes: number[] = []
+  for (let i = 0; i < str.length; ++i) {
+    bytes.push(str.charCodeAt(i))
+  }
+  return bytes
+}
+
+const exampleSendSpontaneousPaymentWithTlvs = async () => {
+  // ANCHOR: send-spontaneous-payment-with-tlvs
+  const nodeId = '...'
+  const extraTlvs: TlvEntry[] = [
+    { fieldNumber: 34349334, value: stringToBytes('Hello world!') }
+  ]
+
+  const sendPaymentResponse = await sendSpontaneousPayment({
+    nodeId,
+    amountMsat: 3000000,
+    extraTlvs
+  })
+  // ANCHOR_END: send-spontaneous-payment-with-tlvs
+}