Static method isn't a thing on this version? (github#17580)

lib/render-content/plugins/use-english-headings.js

@@ -2,6 +2,7 @@ const GithubSlugger = require('github-slugger')
 const Entities = require('html-entities').XmlEntities
 const toString = require('hast-util-to-string')
 const visit = require('unist-util-visit')
+const slugger = new GithubSlugger()
 const entities = new Entities()
 
 const matcher = node => (
@@ -14,12 +15,13 @@ module.exports = function useEnglishHeadings ({ englishHeadings }) {
   if (!englishHeadings) return
   return tree => {
     visit(tree, matcher, node => {
+      slugger.reset()
       // Get the plain text content of the heading node
       const text = toString(node)
       // find English heading in the collection
       const englishHeading = englishHeadings[entities.encode(text)]
       // get English slug
-      const englishSlug = GithubSlugger.slug(englishHeading)
+      const englishSlug = slugger.slug(englishHeading)
       // use English slug for heading ID and link
       node.properties.id = englishSlug
     })