[Readme] Fix test url

[Tyme-Bleyaert]

Fix slashes in url linking to test file, resulting in 404.

[Tyme-Bleyaert]

I'm guessing the WriteLine("Hello World"); in the quickstart example is also out of date?

[ByronMayne]

Thanks for making a PR to fix the docs.

Yeah you are totally right about the example, it should be Logger.Information. Originally it was just write line.