Add exhibitor's guide (#189)

* Add exhibitor's guide

* Update src/sponsors/exhibitor-guide.njk

---------

Co-authored-by: Bhavin Gandhi <[email protected]>

Author: userimack

src/_data/menuItems.json

@@ -65,9 +65,17 @@
     },
     {
         "name": "Sponsors",
-        "link": "sponsors",
-        "hasSubmenu": false,
-        "isExternal": false
+        "hasSubmenu": true,
+        "submenu": [
+            {
+                "name": "Become a Sponsor",
+                "link": "sponsors"
+            },
+            {
+                "name": "Exhibitor Guide",
+                "link": "sponsors/exhibitor-guide"
+            }
+        ]
     },
     {
         "name": "About",