Deprecate GitHub-API

I'd like to open up the discussion around deprecating this package. GitHub itself maintains a great JavaScript client library in [Octokit](https://github.com/octokit/rest.js). I think due to the popularity of our library, it almost hurts the community since we're splitting efforts across multiple projects.

I propose we come up with a rough timeline to deprecating this package and formally recommending people move to Octokit. We could still take security fixes or certain bug fixes for a period of time.

先檢視 issue 討論和連結的 Octokit 專案，以了解提議的遷移方案。只有在棄用時程、安全性或 bug 修正期間，以及此 package 將如何正式引導使用者使用 Octokit 等事項上達成共識後，才算完成。

由索引模型根據 Issue 內容生成。