置顶插件的Github地址。
This plugin adds a back to top button to your GitBook. All three GitBook themes (White, Sepia, Night) are supported.
Add the plugin to your book.json:
{
"plugins" : [ "back-to-top-button" ]
} The back to top button in action:

book.json 
{
"plugins": [
"-lunr",
"back-to-top-button"
]
}
$ gitbook install
info: installing 1 plugins using npm@3.9.2
info:
info: installing plugin "back-to-top-button"
info: install plugin "back-to-top-button" (*) from NPM with version 0.1.4
D:\03 worknote\30 GitBook\*****
`-- gitbook-plugin-back-to-top-button@0.1.4
info: >> plugin "back-to-top-button" installed with success$ gitbook serve
右下角有置顶按钮,点击则会返回顶部。