The standard way for integrating/embedding draw.io is described in https://www.drawio.com/blog/embedding-walkthrough.
It's a protocol via postMessage for load/save. You'd have whatever storage interface there is for cloudron (sorry, I'm not familiar with it) and add a create diagram button. The self-hosted draw.io is shown in an iFrame and saves go back to the parent to store somewhere. That's how pretty much all the integrations works, nextcloud, gitlab, etc.