docs: add documentation for addresstxid event

docs/services/bitcoind.md

@@ -298,12 +298,14 @@ node.services.bitcoind.on('block', function(blockHash) {
 For details on instantiating a bus for a node, see the [Bus Documentation](../bus.md).
 - Name: `bitcoind/rawtransaction`
 - Name: `bitcoind/hashblock`
+- Name: `bitcoind/addresstxid`, Arguments: [address, address...]
 
 **Examples:**
 
 ```js
 bus.subscribe('bitcoind/rawtransaction');
 bus.subscribe('bitcoind/hashblock');
+bus.subscribe('bitcoind/addresstxid', ['13FMwCYz3hUhwPcaWuD2M1U2KzfTtvLM89']);
 
 bus.on('bitcoind/rawtransaction', function(transactionHex) {
   //...
@@ -312,4 +314,9 @@ bus.on('bitcoind/rawtransaction', function(transactionHex) {
 bus.on('bitcoind/hashblock', function(blockhashHex) {
   //...
 });
+
+bus.on('bitcoind/addresstxid', function(data) {
+  // data.address;
+  // data.txid;
+});
 ```