Add Zenduty Integration info to Transports.md docs

[zenbeam]

Adds details around the Zenduty<>LibreNMS integration to the documentation

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[CLAassistant]

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[zenbeam]

Thanks for the approval @ottorei, can we go ahead and merge this?

[librenms-bot]

This pull request has been mentioned on LibreNMS Community. There might be relevant details there:

https://community.librenms.org/t/23-2-0-changelog/20913/1