Installing the nunit.engine adds nunit.engine.nuget.addins to the csproj

[ChrisMaddock]

This isn't intentional. This addins file is just linked to the file in the package itself, which means any edits would be lost on package restore. We probably need to fix this for 3.11.

[CharliePoole]

May just be a doc fix. Users should not edit our addins files but should simply add their own in addition.

[ChrisMaddock]

@jnm2 - I think this has happened with the change to contentFiles. Any idea's how we might prevent this? I've had a dig, but not much luck. 😢

I think we really just want this file to be copied over to bin like the agents - but not be shown as part of the VS project. This is using PackageReference, btw.

[CharliePoole]

This was once confirmed but we need to re-confirm using the latest release.