Resolve "feat(blockchain): Add method to get the current blockheight"

packages/stack/src/blockchain/blockchain-inmemory.ts

@@ -5,6 +5,7 @@ import {
   type BlockchainTransactions,
   type BlockchainUTXO,
   type BlockchainUTXOs,
+  type BlockchainChainTip,
 } from './types.js';
 
 import {
@@ -103,6 +104,12 @@ export class BlockchainInMemory extends BaseBlockchain {
     return blockHeader;
   }
 
+  // TODO: Implement a method for fetching the chain tip.
+  //       This is a placeholder for now.
+  async fetchChainTip(): Promise<BlockchainChainTip> {
+    throw new Error('Not implemented yet');
+  }
+
   async broadcastTransaction(
     tx: Transaction | Uint8Array | string,
     opts: { skipValidation: boolean } = { skipValidation: false },