Format macro options with "smart" typographic punctuation

The marked option `{ smartypants: true }` has been deprecated so we must use `marked-smartypants` here instead

Note: Metalsmith’s `jstransformer-marked` still uses `marked@4.3.0` so we can’t migrate to `marked-smartypants`

markedjs/marked#2766

lib/get-macro-options/index.js

@@ -1,14 +1,18 @@
 const { dirname, join } = require('path')
 
-const { marked } = require('marked')
+const { Marked, Renderer } = require('marked')
+const { markedSmartypants } = require('marked-smartypants')
 
 const { kebabCase, slugify } = require('../nunjucks/filters')
 
 // Get reference to marked.js
-const renderer = new marked.Renderer()
+const renderer = new Renderer()
 // Override marking up paragraphs
 renderer.paragraph = (text) => text
 
+// Custom Marked instance with "smart" typographic punctuation
+const marked = new Marked().setOptions({ renderer }).use(markedSmartypants())
+
 function getMacroOptionsJson(componentName) {
   const optionsFilePath = join(
     dirname(require.resolve('govuk-frontend')),
@@ -45,7 +49,7 @@ function renderNameWithBreaks(option) {
 
 function renderDescriptionsAsMarkdown(option) {
   if (option.description) {
-    option.description = marked(option.description, { renderer })
+    option.description = marked.parse(option.description)
   }
   if (option.params) {
     option.params = option.params.map(renderDescriptionsAsMarkdown)