ts 设计

# Conflicts:
#	build/cxmooc-tools/manifest.json
#	package-lock.json
#	package.json
#	src/config.js
#	yarn.lock

Bump acorn from 6.4.0 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.4.0 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/6.4.0...6.4.1

)

Signed-off-by: dependabot[bot] <support@github.com>

加入下载字幕功能

- 加入下载字幕功能
- 修改了版本号，因为新功能的添加导致不能使用热补丁覆盖
- 感觉在浏览器中打开srt文件挺不优雅的，但是一是跨域、二是HTTP，没想到很好的解决方案