docs: add target blank for all links (#5073)

packages/vant-markdown-loader/src/index.js

@@ -3,6 +3,7 @@ const MarkdownIt = require('markdown-it');
 const markdownItAnchor = require('markdown-it-anchor');
 const frontMatter = require('front-matter');
 const highlight = require('./highlight');
+const linkOpen = require('./link-open');
 const cardWrapper = require('./card-wrapper');
 const { slugify } = require('transliteration');
 
@@ -58,6 +59,7 @@ module.exports = function(source) {
 
   options = {
     wrapper,
+    linkOpen: true,
     ...options
   };
 
@@ -68,5 +70,9 @@ module.exports = function(source) {
     source = fm.body;
   }
 
+  if (options.linkOpen) {
+    linkOpen(parser);
+  }
+
   return options.wrapper(parser.render(source), fm);
 };