LinZhizhao Just took a quick look at your extension, it could very very useful for sure!
In your composer.json, you've allowed all versions of flarum/core below 3.0, but this is not best practice, as your admin JS is not Flarum 2.x compatible.
I'd suggest you edit the core requirement and set ^1.8, which will allow installation on the Flarum 1.x current stable, but not install on 2.x.
To avoid fallback installation, I also suggest to delete the current release tag and re-publish it after you've made the change.
To support Flarum 2.x, take a look at the upgrade docs and run a parallel branch system for 1.x and 2.x. I think supporting 2.x for this extension would likely be very straightforward with only some minor changes.. Let me know if you need any help here!
