Solve the problem that pg cannot be found when 'gdk install' in《安装开发环境帮助文档》

我在按照《安装开发环境帮助文档》步骤安装gdk时，在 gdk install 时出现了下面的报错：

An error occurred while installing pg (1.3.5), and Bundler cannot continue. In Gemfile: activerecord-explain-analyze was resolved to 0.1.0, which depends on pg make: *** [.gitlab-bundle] Error 5 :x:️ ERROR: Failed to install. 2:33 An error occurred while installing pg (1.3.5), and Bundler cannot continue. In Gemfile: activerecord-explain-analyze was resolved to 0.1.0, which depends on pg

经过分析发现是在 gdk install 之前缺少了安装 pg 的步骤

查阅官方文档后找到了对应的解决步骤，为了避免其他人出现相似的问题，我把解决步骤更新在了《安装开发环境帮助文档》中，因此有了这个 mr 。