Added links to user manuals from product page

Author: BenjaminDannegard

content/hardware/04.pro/shields/portenta-uwb-shield/product.md

@@ -2,7 +2,7 @@
 title: Portenta UWB Shield
 url_shop: https://store.arduino.cc/portenta-uwb-shield
 url_guide: /tutorials/
-primary_button_url: /tutorials/
+primary_button_url: /tutorials/01.user-manual
 primary_button_title: Get Started
 core: arduino:mbed_portenta
 forumCategorySlug: '/hardware/portenta/91'

content/hardware/05.pro-solutions/solutions-and-kits/stella/product.md

@@ -2,7 +2,7 @@
 title: Stella
 url_shop: https://store.arduino.cc/
 url_guide: /tutorials/
-primary_button_url: /tutorials/
+primary_button_url: /tutorials/01.user-manual
 primary_button_title: Get Started
 secondary_button_url: /tutorials/
 secondary_button_title: Bootloader Guide