extract the mentions in a ssb message, just using the markdown. this is mostly compatible with the way patchwork does it. but simpler, because it relies only on the markdown.
var mentions = require('ssb-mentions')
var ary = mentions(markdown, opts)
bareFeedNames (boolean, default false): if true, include stub mention
objects for bare feed name mentions, in the format
{name: "NAME", link: "@"}. these can then have the link filled in with a
feed id, to make a "patchwork-style mention", or be removed from the mentions
array before publishing.emoji (boolean, default false): if true, include emoji in the mentions
array, in the form {name: "NAME", emoji: true}.MIT