Properly determine markdown item insertion delimiter

[pokey]

Should inspect the leading item marker to see if they're using - , * , etc to delimit their lists. Don't forget the newline

These seem to behave a bit like indentation. The item content should actually go between the leading delimiter and the newline, just like with indentation. So I don't think we can just treat it like a simple insertion delimiter. We probably should try to find a way to reuse the pieces of editNew that we use for line targets, rather than simple delimiter insertion

A few tests we'll want:

• "bring item air before bat"
• "bring item air after bat"
• "drink item air"