此指令主要是用來啟動 gitbook 的網站服務，會根據變動的檔案即時顯示在網頁中，其指令說明如下
Usage: serve [options] [source_dir]
Options:
-h, --help output usage information
-v, --verbose Activate verbose mode, useful for debugging errors
-o, --output <directory> Path to output directory, defaults to ./_book
-f, --format <name> Change generation format, defaults to site, availables are: site, page, ebook, json
--config <config file> Configuration file to use, defaults to book.js or book.json
-p, --port <port> Port for server to listen on
--no-watch Disable restart with file watching