.NET Core 2.2 Include css and js in nuget package or external dll to hosting project

I am having a problem adding css/js files from my dll to other projects. Problem occurs in 2 situations:

• Different solution includes this nuget package, I only got "shortcuts" of my files, cannot see them, they are not copied, they don't work on server.
• Inside nuget package I have test project, when I include reference to this dll I still cannot use those at all.

How code structure is done:

• project that runs have nothing inside, I have added app.UseMvc(routes => {});

• Dll project (nuget) I am referencing has got all in area admin controller/view/css/js logic

I can enter the controller view without a problem, but I got 404 errors about my static files. Adding app.UseStaticFiles(); doesn't fix the problem.

Can someone tell me how to handle this?