chore: generalized support for code highlighting (#696)

Author: lbertge

Diff for: lib/default-theme/styles/code.styl

@@ -95,7 +95,7 @@ div[class*="language-"]
       background-color $codeBgColor
 
 
-for lang in js ts html md vue css sass scss less stylus go java c sh yaml py
+for lang in $codeLang
   div{'[class~="language-' + lang + '"]'}
     &:before
       content ('' + lang)

Diff for: lib/default-theme/styles/config.styl

@@ -17,5 +17,6 @@ $MQMobileNarrow = 419px
 
 // code
 $lineNumbersWrapperWidth = 3.5rem
+$codeLang = js ts html md vue css sass scss less stylus go java c sh yaml py
 
 @import '~@temp/override.styl'