add Markdown

browser/main/Mixins/Markdown.js

@@ -0,0 +1,12 @@
+var markdownit = require('markdown-it')
+var md = markdownit({
+  typographer: true
+})
+
+var Markdown = {
+  markdown: function (content) {
+    return md.render(content)
+  }
+}
+
+module.exports = Markdown