fix: wrap like Prettier

Compared with Prettier's `--prose-wrap always`, filling differed in
three ways:

- A reference link's text breaks like other text. Only an inline
  link, whose target follows its text, stays on one line.
- A line may start with inline HTML or an autolink. Only a tag that
  can interrupt a paragraph is kept off the start of a line, by the
  same rules as continuation lines. The first line of a paragraph is
  never left as a lone tag, which would start an HTML block.
- A space beside Chinese or Japanese text never breaks, as in
  Prettier, so the words around it fit or move as one. Korean breaks
  at spaces like Latin text.