careers page added to navigation

content/navigation/navigation.md

@@ -140,6 +140,11 @@ navLinks:
         path: https://explorer.threefold.io/
         external: true 
 
+  - name: Join Us
+    link: /careers 
+    external: false
+    expandable: false  
+
 social:
   - icon: telegram-plane
     link: "https://t.me/threefoldnews"