Editorial: make domintro typography more uniform

This implements some of the changes described in whatwg/meta#190 (comment) for our "For web developers (non-normative)" boxes, i.e. "domintro" boxes. Although the first three domintros were rewritten by hand and thus reflect all of those changes, the rest were transformed in an automated fashion, with only the following transformations applied:

* Wrap the entire line in <code> instead of just some property names.
* Remove spaces around dots and parentheses.
* Move ...s before the argument, like JavaScript, instead of after.

Additionally the nature of the automated process involved rewrapping all the <dd> contents, and *un*wrapping all <dt> contents. Some linebreaks were removed and inserted as well to give a consistent style.