Use a class to hold state for Rust GbtGenerator

backend/rust-gbt/index.d.ts

@@ -3,8 +3,11 @@
 
 /* auto-generated by NAPI-RS */
 
-export function make(mempoolBuffer: Uint8Array): Promise<GbtResult>
-export function update(newTxs: Uint8Array, removeTxs: Uint8Array): Promise<GbtResult>
+export class GbtGenerator {
+  constructor()
+  make(mempoolBuffer: Uint8Array): Promise<GbtResult>
+  update(newTxs: Uint8Array, removeTxs: Uint8Array): Promise<GbtResult>
+}
 /**
  * The result from calling the gbt function.
  *