chore: added Open Payment SDK grant menu item (#208)

## Summary
The new Open Payment SDK page must reflect on the grant menu
Fixes INTORG-552

Author: JoblersTune

src/components/pages/FoundationHeader.astro

@@ -125,6 +125,13 @@ import FoundationLogo from '../logos/FoundationLogo.astro'
                 >Grant for the Web</a
               >
             </li>
+            <li class="menu-item menu-item--level-2">
+              <a
+                href="/grant/open-payments-sdk"
+                data-umami-event="Site Nav - Open Payments SDK"
+                >Open Payments SDK</a
+              >
+            </li>
           </ul>
         </li>
         <li class="menu-item has-submenu menu-item--level-1">