LibWeb: Introduce and parse CSS Ratio type

This is only used by media-queries, so for now we can skip
adding/parsing a StyleValue for these.

Userland/Libraries/LibWeb/CSS/Ratio.cpp

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Ratio.h"
+#include <math.h>
+
+namespace Web::CSS {
+
+Ratio::Ratio(float first, float second)
+    : m_first_value(first)
+    , m_second_value(second)
+{
+}
+
+// https://www.w3.org/TR/css-values-4/#degenerate-ratio
+bool Ratio::is_degenerate() const
+{
+    return !isfinite(m_first_value) || m_first_value == 0
+        || !isfinite(m_second_value) || m_second_value == 0;
+}
+
+String Ratio::to_string() const
+{
+    return String::formatted("{} / {}", m_first_value, m_second_value);
+}
+
+auto Ratio::operator<=>(const Ratio& other) const
+{
+    return value() - other.value();
+}
+
+}