LibWeb: Do not allow focusing "Actually Disabled" elements

Author: https://github.com/Simek
Commit: 09420406b8
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2128

Userland/Libraries/LibWeb/HTML/HTMLButtonElement.cpp

@@ -107,4 +107,9 @@ void HTMLButtonElement::activation_behavior(DOM::Event const& event)
     // 4. FIXME: Run the popover target attribute activation behavior given element.
 }
 
+bool HTMLButtonElement::is_focusable() const
+{
+    return enabled();
+}
+
 }