Similar to LadybirdBrowser/ladybird#1714.
We don't implement the linejoin values `miter-clip` and `arcs`, because
according to the SVG 2 spec:
> The values miter-clip and arcs of the stroke-linejoin property are at
> risk. There are no known browser implementations. See issue Github
> issue w3c/svgwg#592.
Nothing uses this yet. The next step is to change
SVGPathPaintable::paint() to read `graphics_element.stroke_linejoin()`
and `graphics_element.stroke_miterlimit()` when painting.
421cf8d9bf