I'm a little uncertain about having this be an object pref vs. a boolean or some combination of other prefs. It makes this a bit more complex to use. That said, I looked at closetag.js and seeing how these options work, I can imagine people reasonably wanting to tweak these different values.

Aside: I wonder why we override indentTags?

One possibility is to start with just a `closeTags` boolean that's either all on (the definition above) or all off and then define other (less likely to be used) preferences to customize the behavior further. I could imagine indentTags being a separate pref, for example.

What do you think?