How to write a local Capacitor plugin which ships own assets?

Question

This local Capacitor plugin has a let's say on-load.js file which will be read and eval-ed by the plugin's Java code, in onPageFinished, even if we've navigated into an external page in our app.

Currently I'm only able to do this if I set up the build to copy the on-load.js into the plugin's consuming Capacitor Android app.
The goal is to make the plugin ship this on-load.js by itself - if that's even possible.