fix(theme): header remove 'position: relative'

[skychx]

Description of the problem:

When using position: relative in the header, the link in the previous line is blocked and cannot be clicked.

Demo

use position: relative

<a href="www.baidu.com">baidu</a>
<h2 className='h2' >header use relative</h2>

.h2 {
    color: #213547;
    box-sizing: border-box;
    position: relative; /* <- this line */
    margin: 3rem 0 1.25rem;
}

.h2:hover {
  background-color: red;
}

h2::before {
  display: block;
  content: ' ';
  height: 70px;
  margin-top: -70px;
}

not use position: relative

<a href="www.baidu.com">baidu</a>
<h2 className='h2' >header not use relative</h2>

.h2 {
    color: #213547;
    box-sizing: border-box;
    /* position: relative;   <- this line */
    margin: 3rem 0 1.25rem;
}

.h2:hover {
  background-color: red;
}

h2::before {
  display: block;
  content: ' ';
  height: 70px;
  margin-top: -70px;
}

[vercel[bot]]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployments, click below or on the icon next to each commit.

vuepress-docs – ./

🔍 Inspect: https://vercel.com/472590061/vuepress-docs/vmhHRp5REqdVpnA2NWzwpJMQCHtE
✅ Preview: https://vuepress-docs-git-fork-skychx-fix-fix-header-style-472590061.vercel.app

vt – ./

🔍 Inspect: https://vercel.com/472590061/vt/CtZMNhjdJTFdZv5rnSYhKsQA2xzD
✅ Preview: https://vt-git-fork-skychx-fix-fix-header-style-472590061.vercel.app

[ulivz]

Close: https://github.com/ulivz/vt/issues/39