This adds initial support for `open-quote`, `close-quote`,
`no-open-quote` and `no-close-quote`. We don't yet track the "nesting
level" so we always use the first pair of quotes from the `quotes`
property.
This fixes the sizing of the arrow icons displayed to the left of
parent sections on a table of contents on Wikipedia articles, which
are sized using the equation `calc(max(0.75em, 12px))`. Now, the icon
will not expand past the edges of the box they are within, avoiding
clipping the edges of the arrows.
These apply to any elements that have some kind of open/closed state.
The spec suggests `<details>`, `<dialog>`, and `<select>`, so that's
what I've supported here. Only `<details>` is fleshed out right now,
but once the others are, these pseudo-classes should work
automatically. :^)
Each ref test now links to its reference page with a link tag, in the
same format as WPT:
`<link rel="match" href="reference-page.html" />`
The reference pages have all been moved into a separate `reference/` dir
so that we can just treat every file in `ref/` as a test. There's no
filter to only look at .html files, because we also have a .svg file in
there, and there may be other formats we want to use too. But it's not
too hard to add one if we need it.
