Original source for the theme switcher came from Luke Lowrey.
But I came up with the favicon switching by sourcing from Stackoverflow, CSS Tricks, and various other places.
If you would rather use png to support older browsers, you can use convertio.co/svg-png.
The one thing I could NOT figure out - how to preload the appropriate favicon based on localStorage. That's why I have favicon.svg set as the default.
If someone could figure that out for me, that would be awesome!