Before this, we were filling and stroking every <path>, whether they had
a fill/stroke color or not. We can avoid a bunch of unnecessary work by
checking if the color is transparent (also the case if unset) before
doing the painting work.
If there is no fill color, we also avoid making a copy of the path to
ensure that it's closed.
Instead of trying to layout SVG boxes as if they are regular CSS boxes,
let's invent an "SVG formatting context" and let it manage SVG boxes.
To facilitate this, Layout::SVGBox no longer inherits from ReplacedBox,
and is instead a simple, "inline-block" style BlockBox.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
