fix: gap between tags and heading1 is too narrow (fix #112)

Author: billyyyyy3320

example/_posts/2018-11-7-frontmatter-in-vuepress-2.md

@@ -8,6 +8,8 @@ author: ULIVZ
 location: Hangzhou  
 ---
 
+# 123 
+
 Any markdown file that contains a YAML front matter block will be processed by [gray-matter](https://github.com/jonschlinkert/gray-matter). The front matter must be the first thing in the markdown file and must take the form of valid YAML set between triple-dashed lines. Here is a basic example:
 
 ```markdown

styles/mobile.styl

@@ -4,9 +4,7 @@
 // @media (max-width: $MQNarrow)
 
 // wide mobile
-@media (max-width: $MQMobile)
-  {$contentClass}:not(.custom) > h1:first-child
-    padding-top 2rem
+// @media (max-width: $MQMobile)
 
 // narrow mobile
 @media (max-width: $MQMobileNarrow)