feat: add broadcast method on esplora blocking client

bdk-android/lib/src/androidTest/kotlin/org/bitcoindevkit/LiveWalletTest.kt

@@ -3,6 +3,7 @@ package org.bitcoindevkit
 import org.junit.Test
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import org.junit.runner.RunWith
+import kotlin.test.assertTrue
 
 @RunWith(AndroidJUnit4::class)
 class LiveWalletTest {
@@ -20,4 +21,38 @@ class LiveWalletTest {
 
         assert(wallet.getBalance().total() > 0uL)
     }
+
+    @Test
+    fun testBroadcastTransaction() {
+        val descriptor = Descriptor("wpkh(tprv8ZgxMBicQKsPf2qfrEygW6fdYseJDDrVnDv26PH5BHdvSuG6ecCbHqLVof9yZcMoM31z9ur3tTYbSnr1WBqbGX97CbXcmp5H6qeMpyvx35B/84h/1h/0h/0/*)", Network.TESTNET)
+        val wallet = Wallet.newNoPersist(descriptor, null, Network.TESTNET)
+        val esploraClient = EsploraClient("https://mempool.space/testnet/api")
+        val update = esploraClient.scan(wallet, 10uL, 1uL)
+
+        wallet.applyUpdate(update)
+        println("Balance: ${wallet.getBalance().total()}")
+        println("New address: ${wallet.getAddress(AddressIndex.New).address}")
+
+        assert(wallet.getBalance().total() > 0uL) {
+            "Wallet balance must be greater than 0! Please send funds to ${wallet.getAddress(AddressIndex.New).address} and try again."
+        }
+
+        val recipient: Address = Address("tb1qrnfslnrve9uncz9pzpvf83k3ukz22ljgees989", Network.TESTNET)
+
+        val psbt: PartiallySignedTransaction = TxBuilder()
+            .addRecipient(recipient.scriptPubkey(), 4200uL)
+            .feeRate(4.0f)
+            .finish(wallet)
+
+        println(psbt.serialize())
+        assertTrue(psbt.serialize().startsWith("cHNi"), "PSBT should start with 'cHNi'")
+
+        val walletDidSign = wallet.sign(psbt)
+        assertTrue(walletDidSign)
+
+        val tx: Transaction = psbt.extractTx()
+
+        println("Txid is: ${tx.txid()}")
+        esploraClient.broadcast(tx)
+    }
 }