[CODEOWNERS] WebPubSub (#21003)
[CODEOWNERS] WebPubSub (#21003)

The focus of these changes is to add the WebPubSub client library and
Functions extension into CODEOWNERS.   Also included is an update to
the Event Hubs service team ownership.
AsrOneSdk/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net