Ordered lists and sublist starts

[Crissov]

I think this was the last thread on the topic, which also discusses several alternatives:

Blank lines before lists, revisited

To weigh in on the proposals: (1) (single-digit start numbers) seems okay to me. It might fix some practical problems (and might cause some others). On the other hand, even with this fix we’d have a mismatch between parser behavior and the spec of the sort described in commonmark/cmark#204. (3) is bad for the reason I just gave in my previous post. One-item lists are, in general, useful, so we don’t want to rule them out altogether. I suppose we could require at least two items when t…