gh-pages， 用于发布gh-pages资源

    默认gh-pages对象

    1. {
    2.   defaults: {
    3.     dest: '.',
    4.     add: false,
    5.     git: 'git',
    6.     depth: 1,
    7.     dotfiles: false,
    8.     branch: 'gh-pages',
    9.     remote: 'origin',
    10.     src: '**/*',
    11.     remove: '.',
    12.     push: true,
    13.     history: true,
    14.     message: 'Updates',
    15.     silent: false
    16.   },
    17.   publish: [Function: publish],
    18.   clean: [Function: clean]
    19. }

    参考： https://www.npmjs.com/package/gh-pages