LibWeb/HTML: Port Window.inner{Width,Height} to IDL

Author: https://github.com/linusg
Commit: 25f53a577d
Pull-request: https://github.com/SerenityOS/serenity/pull/17752
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/Window.idl

@@ -48,6 +48,10 @@ interface Window : EventTarget {
     [NewObject] MediaQueryList matchMedia(CSSOMString query);
     [SameObject, Replaceable] readonly attribute Screen screen;
 
+    // viewport
+    [Replaceable] readonly attribute long innerWidth;
+    [Replaceable] readonly attribute long innerHeight;
+
     // FIXME: Everything from here on should be shared through WindowOrWorkerGlobalScope
     // https://w3c.github.io/hr-time/#the-performance-attribute
     [Replaceable] readonly attribute Performance performance;