Manifest validation tool should detect duplicate Resource Ids for Outlook manifests

[exextoc]

Whenever an Outlook add-in manifest contains duplicate resource IDs, the add-in installs successfully, however, it doesn't show up in the native Windows Outlook and Mac Outlook clients. It, however, shows up in the online Outlook client (Outlook Web Access / OWA).

It will be very helpful if the Office add-in manifest validator could detect duplicate resource IDs.

This request is a result of an actual issue reported by a customer where an add-in which had been successfully validated by the validation tool failed to show up in the native Outlook client.