Update code example in `Readme.md` to reflect changes in a1a5a09
Update code example in `Readme.md` to reflect changes in a1a5a09

wooorm/remark,tanzania82/remarks,ulrikaugustsson/mdast,chcokr/mdast,yukkurisinai/mdast,yukkurisinai/mdast,eush77/remark,chcokr/mdast,eush77/remark,ulrikaugustsson/mdast