ESM Attribute events

ESM Scripts by design do not trigger attr:{propName} events. In order to help migration, it would be helpful to provide some alternative. Something like;

import { Script, watch } from 'playcanvas';

class MyClass extends Script {
    prop = 10;
    
    constructor() {
        watch(this, 'prop');
        this.on('change:prop', console.log);
    }
}

This allows user to attach events and can be applied to any class member, whether an attribute or not.

Any thoughts/input appreciated. @mvaligursky @willeastcott @Maksims @slimbuck