fix: update to new highlight api

See highlightjs/highlight.js#2277

core.js

@@ -12,7 +12,7 @@ const registerLangs = (hljs, register) => register &&
 
 // Highlight with given language.
 const highlight = (hljs, code, lang) =>
-  maybe(() => hljs.highlight(lang || 'plaintext', code, true).value) || ''
+  maybe(() => hljs.highlight(code, { language: lang || 'plaintext', ignoreIllegals: true }).value) || ''
 
 // Highlight with given language or automatically.
 const highlightAuto = (hljs, code, lang) =>