allow listen directive to listen to multiple outputs at once

[electrovir]

something like this:

<${MyElement}
    ${listen(MyElement, {
        [MyElement.events.eventName]: (event) => {
            doSomething(event);
        },
        [MyElement.events.otherEventName]: (event) => {
            doSomethingElse(event);
        },
    })}
>
</${MyElement}>

[electrovir]

I don't think it'll be possible to support this while maintaining type safety, but I'll keep it open to encourage trying again in the future.