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>

frontend/src/app/components/block/block.component.html

@@ -114,6 +114,11 @@
                   <td i18n="block.nonce">Nonce</td>
                   <td>{{ block.nonce | decimal2hex }}</td>
                 </tr>
+                <tr>
+                  <td i18n="block.header">Block Header Hex</td>
+                  <td><a target="_blank" href="/api/block/{{block.id}}/header" title="click to view">view</a> </td>
+                  
+                </tr>
               </tbody>
             </table>
           </div>