qmk_firmware_custom/book.json

{
    "structure": {
        "readme": "Home.md"
    },
    "plugins" : ["toolbar", "edit-link"],
    "pluginsConfig": {
            "edit-link": {
                "base": "https://github.com/qmk/qmk_firmware_docs/edit/master",
                "label": "Suggest an edit"
            },
        "toolbar": {
            "buttons":
            [
                {
                    "label": "QMK Firmware",
                    "icon": "fa fa-github",
                    "url": "https://github.com/qmk/qmk_firmware"
                }
            ]
        }
    }
}