Hello Lewis!
Thanks! I'm happy you liked it
I second what @Stachu said. You can use Exact Audio Copy to rip your CDs to flac or wav or mp3.... all these formats are supported by the minidisc app. I've also found a quick guide that should help you to get started https://www.techradar.com/how-to/how-to-rip-your-cds-to-flac . I fear that direct CD access is something that browsers cannot really do for now. However, I'll make some research and see if there's a way to do that.
To encode the music I've used an external library that currently does not support atrac3+ (https://github.com/dcherednik/atracdenc/). However, I know that the guy who's developing this library has been asked to support atrac3+ as well. I'll keep an eye on his project and make sure to bring atrac3+ support in case he decided to add it to his library.