fix: check for wallet tx batching support

lib/plugins/wallet/bitcoind/bitcoind.js

@@ -170,6 +170,11 @@ function fetchRBF (txId) {
     })
 }
 
+function supportsBatching (account, cryptoCode) {
+  return checkCryptoCode(cryptoCode)
+    .then(() => _.isFunction(sendCoinsBatch))
+}
+
 module.exports = {
   balance,
   sendCoins,
@@ -179,5 +184,6 @@ module.exports = {
   cryptoNetwork,
   fetchRBF,
   estimateFee,
-  sendCoinsBatch
+  sendCoinsBatch,
+  supportsBatching
 }