LibWeb: Stub out all the functions from the execCommand spec

Per the specification, it's ok if we say that nothing is supported.

It's not ok if we say something is supported but do nothing, apparently.

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -2987,13 +2987,6 @@ void Document::did_stop_being_active_document_in_navigable()
     }
 }
 
-// https://w3c.github.io/editing/docs/execCommand/#querycommandsupported()
-bool Document::query_command_supported(String const& command) const
-{
-    dbgln("(STUBBED) Document::query_command_supported(command='{}')", command);
-    return false;
-}
-
 void Document::increment_throw_on_dynamic_markup_insertion_counter(Badge<HTML::HTMLParser>)
 {
     ++m_throw_on_dynamic_markup_insertion_counter;
@@ -4076,4 +4069,40 @@ WebIDL::ExceptionOr<JS::Value> Document::named_item_value(FlyString const& name)
     return collection;
 }
 
+// https://w3c.github.io/editing/docs/execCommand/#execcommand()
+bool Document::exec_command(String, bool, String)
+{
+    return false;
+}
+
+// https://w3c.github.io/editing/docs/execCommand/#querycommandenabled()
+bool Document::query_command_enabled(String)
+{
+    return false;
+}
+
+// https://w3c.github.io/editing/docs/execCommand/#querycommandindeterm()
+bool Document::query_command_indeterm(String)
+{
+    return false;
+}
+
+// https://w3c.github.io/editing/docs/execCommand/#querycommandstate()
+bool Document::query_command_state(String)
+{
+    return false;
+}
+
+// https://w3c.github.io/editing/docs/execCommand/#querycommandsupported()
+bool Document::query_command_supported(String)
+{
+    return false;
+}
+
+// https://w3c.github.io/editing/docs/execCommand/#querycommandvalue()
+String Document::query_command_value(String)
+{
+    return String {};
+}
+
 }