NuGet package doesn't copy file to destination project

Question

I create a NuGet package with all components that I need to reuse in some project. In the project with components I have some .less and .js files. I need to copy these files in wwwroot of my projects when I install my NuGet package. I tried with contentFiles and files tags but nothing works:

<contentFiles>
    <files include="**/wwwroot/**" buildAction="Content" copyToOutput="true" />
</contentFiles>

Or with files:

<files> 
    <file src="contentFiles\**" target="contentFiles" /> 
    <file src="wwwroot\**" target="wwwroot" />
    <file src="**\wwwroot\**" target="wwwroot" /> 
</files>

There is some tries. Nothing works. Is possible to do what I want?

These files don't even appear in the final build. .less file must be copied in project because they have an import of a base file with constants which could change in different projects. .js files can also appear only in the compiled.

With NuGet Package Explorer I tried to create contentFolder similar to this example https://stackoverflow.com/a/52418304/5731129. I created subfolders and add an image, bbut after installation the file was not copied.