This resource pack fixed the unusable URL images within Action forms when using Script API.
It is actually pretty simple! It uses the newly discovered profile_image_renderer that allows resource packs to display URL images without the Action form button to explicitly be in the URL format, which Script API does not support.
All you need to do is add the resource pack in the latest release, or use the source code to implement the renderer yourself! Just that simple! No need for external plugins or software.