List App on the Github app marketplace

---- **NOTE: CANNOT PROCEED UNTIL APP HAS 250 INSTALLATIONS** ----

As a developer of the github-backup Github app
I want to list the app on the Github marketplace
So that users can found the app and install it directly from the marketplace.

## Requirements


Link to the requirements for the app to be listed on the marketplace: https://developer.github.com/apps/marketplace/listing-apps-on-github-marketplace/requirements-for-listing-an-app-on-github-marketplace/

From an MVP view we might not want to publish the app straight away to the marketplace (especially if the app is not allowed in beta and that a paid version should be defined) however we need to review all the list of requirements to make sure that the app will be able to be published

首先查看所链接的 GitHub Marketplace 上架要求，以及 issue 中提出的 250 次安装这一前置条件。尚未确定任何源文件或测试；要视为完成，需要确认 github-backup 应用满足哪些要求，以及在继续进行 Marketplace 上架之前还需要完成哪些工作。

由索引模型根据 Issue 内容生成。