Docs needed to explain how to use IoTHub Trigger

We expose IoTHub Trigger as a concept in VS2017, CLI and VSCode, however searching for it on docs.microsoft.com yields zero results. There is no tutorial, reference topic or any mention at all. Having docs on this is critical because it is not obvious how to configure it correctly with the connection strings - especially in the light of the breaking change between V1 and V2 here.

We should strive to:
1) have a dedicated topic similar to this one https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-event-hubs
2) mention it here like all the other triggers: https://docs.microsoft.com/en-us/azure/azure-functions/functions-overview
3) mention it here https://docs.microsoft.com/en-us/azure/azure-functions/functions-triggers-bindings
4) mention it here https://docs.microsoft.com/en-us/azure/azure-functions/functions-run-local#create-func
5) mention it here https://docs.microsoft.com/en-us/azure/azure-functions/functions-develop-vs