Add Azure App Service to the Host and deploy topic

[guardrex]

Because this isn't a tutorial, let's try to avoid screenshots if possible and just provide a list of steps with links out to other topics if/when it makes sense ... especially to our aspnet/Docs topics:

• https://docs.microsoft.com/aspnet/core/host-and-deploy/azure-apps/
• https://docs.microsoft.com/aspnet/core/host-and-deploy/azure-apps/troubleshoot (but this only applies to the server-side ASP.NET Core bits)

[guardrex]

The topic contains enough content on this point to stand as-is for now.