Fix audio speed reset on song change

[BlobCodes]

The fix was taken from https://github.com/vixalien/decibels/issues/44#issuecomment-1858681404.

I applied the change and built the app using gnome builder, where everything worked perfectly.

[vixalien]

Thank you. The final step is to add your name for credit.

Please rebase and then add your name here:

https://github.com/vixalien/decibels/blob/b5fa774e51b6e070791c42c203ab1276a7d1ba9d/src/application.ts#L42-L44

[BlobCodes]

Thank you. The final step is to add your name for credit.

I rebased the branch and added the name. (Even though I didn't really do anything, just copied the fix from you)

[vixalien]

Thank you very much!!!