Update VS instructions to include preview install steps

[jongio]

Let's add steps on how to get the right VS preview version installed
https://docs.microsoft.com/en-us/azure/developer/azure-developer-cli/debug?tabs=windows&pivots=ide-vs#enable-the-preview-feature

[rajeshkamal5050]

@jongio since it is a P2. Moving it to backlog. Please pull it in if you think otherwise.

[jongio]

I was thinking this would be @puicchan as she is doing doc updates.

[puicchan]

@savannahostrowski - can you help to provide the right information here?