feature: 新增可配置化的 帮助中心 页面

[wangliang181230]

Ⅰ. 描述此PR的作用：

feature: 新增可配置化的 帮助中心 页面

可通过 help.dataList 配置项进行配置，也可配置在远程配置文件中：

{
  "help": {
    "dataList": [
      {
        "title": "1、主题xxxx",
        "children": [
          {
            "title": "1）标题标题标题标题标题",
            "url": "https://github.com/docmirror/dev-sidecar/wiki"
          }
        ]
      },
      {
        "title": "2、主题yyyy",
        "children": [
          {
            "title": "1）标题1",
            "url": "https://github.com/docmirror/dev-sidecar/wiki"
          },
          {
            "title": "2）标题标题标题标题标题",
            "url": "https://github.com/docmirror/dev-sidecar/wiki"
          }
        ]
      },
      {
        "title": "3、主题zzzz",
        "children": [
          {
            "title": "1）标题1",
            "url": "https://github.com/docmirror/dev-sidecar/wiki"
          },
          {
            "title": "2）标题标题标题标题标题",
            "url": "https://github.com/docmirror/dev-sidecar/wiki"
          },
          {
            "title": "3）标题标题标题标题标题",
            "url": "https://github.com/docmirror/dev-sidecar/wiki"
          }
        ]
      }
    ]
  }
}

Ⅱ. 此PR修复了哪个issue吗？

fixes #404

Ⅲ. 界面变化截屏