chore: added export to index.ts

Issue: BTC-2150

TICKET: BTC-2150

Author: christopher-fong

modules/utxo-lib/src/index.ts

@@ -1,5 +1,7 @@
 export * from 'bitcoinjs-lib';
 
+export * as varuint from 'bitcoinjs-lib/src/bufferutils';
+
 export * as bitgo from './bitgo';
 
 export * as address from './address';