Support for Xiaomi App Store

Support for Xiaomi App Store 小米应用商店 would be very useful!

It may be possible to scrape corresponding metadata from the website, which contains rankings, download counts, which you can derive from the package name: `https://app.mi.com/details?id=`

However, for non-game applications, most of these pages' direct download links don't work. The "direct download" button says "under maintenance" (维护中), so this might need some more work.