Merge pull request #8 from commenthol/fix-undef-lang

fix: console log Unknown language: ""

index.js

@@ -10,7 +10,7 @@ const maybe = f => {
 
 // Highlight with given language.
 const highlight = (code, lang) =>
-  maybe(() => hljs.highlight(lang, code, true).value) || ''
+  maybe(() => hljs.highlight(lang || 'plaintext', code, true).value) || ''
 
 // Highlight with given language or automatically.
 const highlightAuto = (code, lang) =>