[core] extend color.ini functionality to PIP windows

Provide a description of the new feature

Spotify for Windows (64 Bit) 1.2.31.1205.g4d59ad7c Spicetify v2.31.3

Since there is a new pip player activated in the new spotify release it would be great if themes had an easy way to change its colors to fit the theme. Dark grey with black songtitle and black buttons just looks bad and is not very readable.

➕ Additional Information

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