Add Analyzers "Warnings as Errors" example to quick start

[jonmotos]

It would be very handy to see in the quick-start the necessary csproj configuration to produce build errors instead of warnings with the included Analyzers!

Happy to create a PR.

[martinothamar]

Sure, feel free 👍 are you thinking of TreatWarningsAsErrors or adjusting them through .editorconfig or something?

[jonmotos]

Yea I was thinking like the following - just gotta find the right warnings.

<WarningsAsErrors>0219,CS0168</WarningsAsErrors>

[yvanlo]

Hi! I'd like to pick this up. I opened a PR that documents both WarningsAsErrors and .editorconfig severity, with the list of diagnostic IDs.