docfix/added VITE_OBP_API_DEFAULT_RESOURCE_DOC_VERSION to .env.example

Author: hongwei1

.env.example

@@ -8,6 +8,9 @@ VITE_OBP_API_PORTAL_HOST=https://apisandbox.openbankproject.com
 ####################################################################################
 
 VITE_OBP_API_VERSION=v5.1.0
+#The default version of the root page, it has the default value `OBP+VITE_OBP_API_VERSION`
+#The format must follow standard+Version, e.g., OBPv5.1.0, BGv1, or BGv1.3.
+#VITE_OBP_API_DEFAULT_RESOURCE_DOC_VERSION=OBPv5.1.0
 VITE_OBP_API_MANAGER_HOST=https://apimanagersandbox.openbankproject.com
 VITE_OBP_API_EXPLORER_HOST=http://localhost:5173
 VITE_OBP_CONSUMER_KEY=your_consumer_key