[Feature] A way to set custom icon paths for the Mpris widget.

[ItsTerminal]

I use trizen/youtube-viewer to play music and videos and this scrapes youtube urls and so cannot provide cover art, i have however found a way to automatically download the cover art for each video using wget, the problem is that the mpris widget automatically sets the mpv logo instead of cover art, I need a way to set a custom icon path in the config to use as a fallback.
I think this is a feature that could be quite useful for others and not just me as it allows for greater customization and icon overrides for certain music players.