LibWeb: Add ShadowRoot.clonable and ShadowRoot.serializable

Author: https://github.com/awesomekling
Commit: 8e68215d33
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/278
Reviewed-by: https://github.com/mattco98
Reviewed-by: https://github.com/nico

Userland/Libraries/LibWeb/DOM/ShadowRoot.idl

@@ -8,6 +8,8 @@ interface ShadowRoot : DocumentFragment {
     readonly attribute ShadowRootMode mode;
     readonly attribute boolean delegatesFocus;
     readonly attribute SlotAssignmentMode slotAssignment;
+    readonly attribute boolean clonable;
+    readonly attribute boolean serializable;
     readonly attribute Element host;
     attribute EventHandler onslotchange;
 };