[docs] Update nlog.md for Alternate NLog Configuration

[james-Solutions]

Adding an Alternate Configuration for NLog Elastic APM. Using the example provided from the Nuget website.

https://www.nuget.org/packages/Elastic.Apm.NLog

[cla-checker-service]

💚 CLA has been signed

[github-actions]

👋 @james-Solutions Thanks a lot for your contribution!

It may take some time before we review a PR, so even if you don’t see activity for some time, it does not mean that we have forgotten about it.

Every once in a while we go through a process of prioritization, after which we are focussing on the tasks that were planned for the upcoming milestone. The prioritization status is typically reflected through the PR labels. It could be pending triage, a candidate for a future milestone, or have a target milestone set to it.

[james-Solutions]

❌ Author of the following commits did not sign a Contributor Agreement: 7fe3bc3

Please, read and sign the above mentioned agreement if you want to contribute to this project

This should be signed now.

[github-actions]

🔍 Preview links for changed docs

• docs/reference/nlog.md

[stevejgordon]

run docs-build