docs: add huaweicloud to website sidebar navigation

Register the new provider in website/sidebars.json so the
HuaweiCloud node documentation appears in the site navigation,
as required by CONTRIBUTING.md.

website/sidebars.json

@@ -29,7 +29,8 @@
       "nodes/saas",
       "nodes/c4",
       "nodes/custom",
-      "nodes/gis"
+      "nodes/gis",
+      "nodes/huaweicloud"
     ]
   }
 }