refactor: simplify regexp and reserve escaped '`'

Author: ulivz

lib/util/parseHeaders.js

@@ -13,12 +13,9 @@ const unescapeHtml = html => String(html)
   .replace(/>/g, '>')
 
 const removeMarkdownToken = str => String(str)
-  .replace(/`(.*)`/, '$1')  // ``
-  .replace(/\[(.*)\]\(.*\)/, '$1')  // []()
-  .replace(/\*\*(.*)\*\*/, '$1')  // **
-  .replace(/\*(.*[^\\])\*/, '$1')  // *
-  .replace(/_(.*[^\\])_/g, '$1')  // _ _
-  .replace(/(\\)(\*|_)/g, '$2') // remove escaped char '\'
+  .replace(/\[(.*)\]\(.*\)/, '$1')            // []()
+  .replace(/(`|\*\*|\*|_)(.*[^\\])\1/, '$2')  // `{t}` | *{t}* | **{t}** | _{t}_
+  .replace(/(\\)(\*|_|`)/g, '$2')             // remove escape char '\'
 
 exports.removeTailHtml = (str) => {
   return String(str).replace(/<.*>\s*$/g, '')