Change release file type crx to zip

[shellvon]

Since I only need a zip file when I published this extension by use the Chrome Web Store Background. It's very convenient for me to runnpm run build-zip. But when I use GitHub to release the app I need to manually package crx, which is cumbersome to operate, so I plan to start from the 1.0.4 version I no longer package crx but directly only provide zip file to download.

由于每次 Chrome 后台发布只需要zip文件，我只运行npm run build-zip很方便，但是 Github 发布我却需要手动打包 crx, 操作起来繁琐，因此目前计划从 1.0.4 版本开始不再由我打包CRX而是直接提供下载zip自行解包安装。