There should be a simple minimal example. Ideally this would also only use options not planned to be deprecated in the future, but promoting the use of the icon version only might break with some skins for now. I'm relatively new to MediaWiki and thus not editing the Manual directly, but this is my proposal:
$wgLogos = [
'1x' => "path/to/1x_version.png", // path to 1x version
];