optimization: hash lookup is faster than in-array check (github#23079)

lib/render-content/plugins/rewrite-local-links.js

@@ -10,7 +10,7 @@ import removeFPTFromPath from '../../remove-fpt-from-path.js'
 import readJsonFile from '../../read-json-file.js'
 const supportedVersions = Object.keys(allVersions)
 const supportedPlans = Object.values(allVersions).map((v) => v.plan)
-const externalRedirects = Object.keys(readJsonFile('./lib/redirects/external-sites.json'))
+const externalRedirects = readJsonFile('./lib/redirects/external-sites.json')
 
 // Matches any <a> tags with an href that starts with `/`
 const matcher = (node) =>
@@ -41,7 +41,7 @@ function getNewHref(node, languageCode, version) {
   // Exceptions to link rewriting
   if (href.startsWith('/assets')) return
   if (href.startsWith('/public')) return
-  if (externalRedirects.includes(href)) return
+  if (href in externalRedirects) return
 
   let newHref = href
   // If the link has a hardcoded plan or version in it, do not update other than adding a language code