There are many installations on the map that are drawn with rect
instead of path. I could transform them with Inkscape, but i finally
found out about DOMMatrix, that helps me a lot to convert points, as
it can parse the values of the `transform` attribute.
I also saw that SVGGraphicElements has getCTM() and getScreenCTM(), but
neither of them worked for me: the resulting transformation was “shrunk”
on the map (i.e., like it was scaled down).