book.json

{
    "root": "txt",
    "plugins":  ["-toc", "-video"],
    "pluginsConfig": {
        "toc": {
            "addClass": true,
            "className": "toc",
            "maxDepth": 6
        },
         "toolbar": {
            "buttons":
            [
                {
                    "label": "GitHub",
                    "icon": "fa fa-github",
                    "url": "https://github.com/"
                },
                {
                    "label": "Search page title on StackOverflow",
                    "icon": "fa fa-stack-overflow",
                    "url": "http://stackoverflow.com/search?q={{title}}"
                },
                {
                    "label": "Share link on Facebook",
                    "icon": "fa fa-facebook",
                    "url": "http://www.facebook.com/sharer/sharer.php?s=100&p[url]={{url}}"
                },
                {
                    "label": "Share page title and link on Twitter",
                    "icon": "fa fa-twitter",
                    "url": "http://twitter.com/home?status={{title}}%20{{url}}"
                }
            ]
        }
    }
}