feat: support embedded album art covers

[turtletowerz]

This adds complete support for embedded album art for any format that TagLib supports.

I'm marking this as a draft because there are a few code considerations I would like to get input on before continuing:

1. The relevant audiotags package changes need to be made to sentriz/audiotags instead of linking to my personal repo. I did this for testing reasons but it will be removed before this is actually committed
2. The way the cover cache path is passed around feels janky, and im wondering if there should be a more intentional settings or shared variables package.
3. All of the embedded logic is shoved into tagcommon; not sure if this is appropriate or not

closes #11