Packaging
The add-on files must be packed in ZIP format and its filename must use the .zip extension. The resulting ZIP file can contain a root folder. The name of that folder is not meaningful. Such a ZIP archive can be uploaded to the Platform Setup Application using the provided form in the Add-ons page.
Here is a sample directory structure for the ZIP archive:
> tree dashboardportlet/ dashboardportlet/ css/ dashboardportlet.css js/ dashboardportlet.js manifest.json 2 directories, 3 files