Added missing block header API (#630)

* header API frontend

* Block Header API endpoint added to Node.js backend

* updated package-lock.json

Co-authored-by: Rishabh <rishabh@Rajeshs-MacBook-Pro.local>

backend/src/routes.ts

@@ -506,6 +506,15 @@ class Routes {
     }
   }
 
+  public async getBlockHeader(req: Request, res: Response) {
+    try {
+      const blockHeader = await bitcoinApi.$getBlockHeader(req.params.hash);
+      res.send(blockHeader);
+    } catch (e) {
+      res.status(500).send(e.message || e);
+    }
+  }
+
   public async getBlocks(req: Request, res: Response) {
     try {
       loadingIndicators.setProgress('blocks', 0);