add build (npm run build) of wysiwg client folder to build process

[idseefeld]

In the past I had sometime the issue, that not all js file from the \wwwroot\App_Plugins\WysiwgUmbracoCommunityExtensions folder were not up to date or even missing in the NuGet package. Currently they need to be in the repository, but it would be even better to run the build during package generation.
Therefor I need to add this build step in the Github action. Or could this be done with a prebuild step in msbuild?

[idseefeld]

I have added npm run bulid to project wysiwgUmbracoCommunityExtensions.csproj PreBuild target and removed wwwroot folder from repo.