feat(abstract-utxo): export BitGoPsbt type from transaction module

Export the BitGoPsbt type from wasm-utxo to make it available to
consumers of the abstract-utxo module.

Issue: BTC-2768

Co-authored-by: llm-git <llm-git@ttll.de>

Author: OttoAllmendinger

modules/abstract-utxo/src/transaction/types.ts

@@ -5,6 +5,8 @@ import type { UtxoNamedKeychains } from '../keychains';
 
 import type { CustomChangeOptions } from './fixedScript';
 
+export type BitGoPsbt = fixedScriptWallet.BitGoPsbt;
+
 export type SdkBackend = 'utxolib' | 'wasm-utxo';
 
 export function isSdkBackend(backend: string): backend is SdkBackend {