I am following the documentation  to test my custom widget in the Widgets playground. Whenever I try to load my custom widget I get a balloon with NetworkError when attempting to fetch resource, and I don't even see a request coming in in my localhost server. This server is serving through https, and I can access it by going to https://localhost:port directly without any problems.
I am serving the contents of my folder that contains just index.html, index.js, and manifest.json. Zipping that folder and uploading it as a custom widget does work - but is too much of a hassle for development - so I am quite sure that my widget itself is working correctly.
Any tips for setting this widget up in the Widgets playground?