Github repos are weird in that they technically do not host your CSS as a static file. This means you are unable to at-import them. However, you can enable Github pages which allows you to host the raw static file, allowing you to at-import them.
What you do is go into the settings of your repo and scroll down to Github Pages. From there make the ‘Source’ your master branch. It should then inform you that your project is now published at a Github Pages url that looks like https://bixgit.github.io/bixblog/.
Now add the file to the route so it looks like: https://bixgit.github.io/bixblog/bixblog.css. Then you should be able to at-import it.
But besides that, does the search functionality in the app work for your use case?