Add getter for prefers color scheme value found on Device (#100)

* add getter for prefers color scheme value found on Device

* update doc comment

Co-authored-by: Martin Robinson <mrobinson@igalia.com>
Signed-off-by: arthmis <artmis9@protonmail.com>

---------

Signed-off-by: arthmis <artmis9@protonmail.com>
Co-authored-by: lazypassion <25536767+lazypassion@users.noreply.github.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

Author: arthmis

style/servo/media_queries.rs

@@ -301,6 +301,11 @@ impl Device {
         AbsoluteColor::BLACK
     }
 
+    /// Returns the color scheme of this [`Device`].
+    pub fn color_scheme(&self) -> PrefersColorScheme {
+        self.prefers_color_scheme
+    }
+
     pub(crate) fn is_dark_color_scheme(&self, _: ColorSchemeFlags) -> bool {
         false
     }