Add getBlockHeader method.

examples/nodejs/index.ts

@@ -0,0 +1,17 @@
+import mempoolJS from "@mempool/mempool.js";
+
+const init = async () => {
+    const { bitcoin } = mempoolJS({
+        hostname:'mempool.ninja'
+    });
+    
+    const feesRecommended = await bitcoin.fees.getFeesRecommended();
+    console.log(feesRecommended);
+
+    const hash = "0000000000000000000065bda8f8a88f2e1e00d9a6887a43d640e52a4c7660f2";
+    const block = await bitcoin.blocks.getBlockHeader({hash});
+
+    console.log(block);
+};
+
+init();