[Enhancement]: Do not fetch entire library when you add or remove a song

[kgarner7]

The feature you would like

Currently, when you add or remove a song from the library, it triggers a full fetch of the library, which for large libraries can take a long time. It would be nice if, instead of updating the entire library, you can just append/remove the new song.

Alternatives and Other Information

I'm not too familiar with the musickit API, but the .song() and .album() should probably be able to fetch the correct resource and just add/remove it? I'll probably take a look later to see what it would take

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