启动项目后报link未定义，首页无法显示

[lanwp530]

Describe the bug
启动应用后，应用正常启动。但是进入首页后报如下错误，link未定义页面无法正常显示：

To Reproduce
Steps to reproduce the behavior:

1. 启动应用。
2. 正常启动后访问首页

Expected behavior
A clear and concise description of what you expected to happen.

System Info

• VuePress version: 1.8.2
• Antdocs version: 1.3.4
• Node version: v14.16.0
• OS version: win10 （Microsoft Windows [版本 10.0.16299.15]）

node package.json引用依赖

"devDependencies": {
    "@vuepress/plugin-active-header-links": "^1.5.4",
    "@vuepress/plugin-back-to-top": "^1.5.4",
    "@vuepress/plugin-nprogress": "^1.5.4",
    "vuepress": "^1.5.4",
    "vuepress-plugin-permalink-pinyin": "^1.0.0"
  },
  "dependencies": {
    "vuepress-theme-antdocs": "^1.3.4"
  }

Additional context
Add any other context about the problem here.

[zpfz]

antdocs v1.3.4 做了一些破坏性变动，需要将首页的 README.md 中首页按钮配置进行修改，例：

actionBtn:
  text: Get Started
  link: /guide/
  type: primary
  ghost: false
  size: large
preactionBtn:
  text: Playground
  link: /guide/
  type: primary
  ghost: true
  size: large

详情见：首页按钮，另外 antdocs 近期更新详情见：更新日志。
目前不建议使用 vuepress-creator 创建项目，请等待 vuepress-creator 更新后再使用。

[xkloveme]

缺少首页配置项导致,我提交了pr,请作者合并

[zpfz]

缺少首页配置项导致,我提交了pr,请作者合并

已合并更新，感谢你的PR哈！