Create an SVG File with the proportions 10:3 e.g. in Adobe Illustrator or google draw

Edit the file in a text editor and add the following text to the top of the File

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"
"http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">

Add to the site in the Site manager

There are two logo types. Background light, background dark.

Enjoy