Turn the player slider into a loading progress bar when loading songs

[ghost]

Checklist

• I've checked that there is no other issue about this feature request.
• This issue contains only one feature request.
• The title of this issue accurately describes the feature request.

Feature description

The player slider should turn into a loading indicator which indicates how much of the current song has loaded.

Why do you want this feature?

It is a clever way to show loading progress. The player slider isn't currently very important when loading songs.

Additional information

No response