v0.4.0

Attention: The new Modern Mode is unstable when you type fast, and it explicitly leads to higher performance cost, so we recommend use Classic Mode (previously Editor Mode). But we consider it as a useful new feature, so we will explore how to optimize it to provide better experience for users of this extension later.

1. #35 : Change Reader Mode to Modern Mode - mark foldable blocks with cover-rows-count instead of end-line-number, and make it auto-update on input.
2. #37: Call moveCursor with class singleton to avoid undefined error.