diagnostics: add aspnet core example

[Pondidum]

Small addition to the documentation to show how to call WhatDidIScan() and WhatDoIHave() when running in ASP.Net core, based off @CodingGorilla's comment here

[CodingGorilla]

To be clear, the env.IsDevelopment() is not required, I choose to only run those two methods when my app is running in a development or staging environment and not on production.

[Pondidum]

Yes, I was in two minds whether to include it or not, but it felt like a more complete example the .IsDevelopment call included.
I don't mind removing it if you think it's cluttering the example :)

[jeremydmiller]

Got it and thank you. I'll have this up soon-ish.