With the newly supported fuzzy matching in our test-web runner, we can
now define the expected maximum color channel and pixel count errors per
failing test and set a baseline they should not exceed.
The figures I added to these tests all come from my macOS M4 machine.
Most discrepancies seem to come from color calculations being slightly
off.
This has been left unimplemented since we switched to the Skia renderer.
Now `text-decoration-style: wavy` actually paints a wavy line. :^)
We had a text-decoration test, but it only checked `solid` lines, so
I've replaced it with a modified version of the old test page from
Serenity, without the blink option, and with some thickness parameters.
I did experiment with using a `SkPath1DPathEffect` to make it repeat the
pattern for us, but I couldn't make it look good at all.