Reexamine the public path cdn

[jasongrout]

Right now, we hardcode the unpkg CDN in the public path of the amd module in the dist/ directory:

widget-cookiecutter/{{cookiecutter.github_project_name}}/js/webpack.config.js

Line 69 in 9694718

publicPath: 'https://unpkg.com/{{ cookiecutter.npm_package_name }}@' + version + '/dist/'

I think we should:

1. Figure out if we still need to hardcode it with webpack 5's automatic public path code
2. If we still need to hardcode it, change it to jsdelivr to match what we are doing in ipywidgets 8.

[jasongrout]

This was fixed in #103