Add a JavaScript object feature

[Elchi3]

The feature id here is object-object to not clash with the already existing object id (the HTML element)

All keys are baseline high but we could probably have a discussion if some of the more later additions should be their own features.

[ddbeck]

Yes, I've thought about it for a bit.

So, I'd like to have "inner" slices on the feature, so we can have snapshots for ES5 and ES6. But it's hard to really make the case for that except as a historic marker. I think we can proceed as is.

[ddbeck]

Surely this should be [object Object], with the filename object-object.yml? 😂

I'm only joking. Mostly.

[Elchi3]

hm, actually I like object-object.yml as the ID here. Should we do that?

[ddbeck]

Yes, let's do it! After sleeping on it, I like giving these things more distinctive names.