Add-on that lists all the already installed add-ons on the gateway

I would like to know if is it possible to write an add-on that lists all the already installed add-ons (or those that are in execution) on the gateway.
From where should I start If I want to write such an add-on in JS? Which are the main things to pay attention to during the writing process?

I have already skimmed the documentation and the API/libraries and I did not found a clue about it…

Yes, this is possible. Have a look at the Candle App Store addon for an example of this.

I apologize in case I missed something obvious, but WebThings shows what addons are installed and/or enabled (running unless disabled) in:

Settings -> Addons

Basically, what I was looking for was a way to obtain the list in JSON format in order to update this list elsewhere. Starting from the example extension found in the documentation, I wrote my own extension to do this, and I eventually did the trick by calling in the Extension subclass an undocumented API of the gateway.