LibWeb: Add WebIDL to the IDL generator's list of web namespaces

Without this, the generated DOMExceptionConstructor does not refer to
the WebIDL::DOMException with its fully qualified name. This caused an
ambiguity error on my machine.

Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/main.cpp

@@ -93,6 +93,7 @@ int main(int argc, char** argv)
         "UIEvents"sv,
         "URL"sv,
         "WebGL"sv,
+        "WebIDL"sv,
         "WebSockets"sv,
         "XHR"sv,
     };