LibJS: Add Boolean constructor object

Author: https://github.com/jack-karamanian
Commit: edae926cb0
Pull-request: https://github.com/SerenityOS/serenity/pull/1682
Reviewed-by: https://github.com/bgianfo

Libraries/LibJS/Runtime/Object.h

@@ -59,6 +59,7 @@ public:
     void put_native_property(const FlyString& property_name, AK::Function<Value(Interpreter&)> getter, AK::Function<void(Interpreter&, Value)> setter);
 
     virtual bool is_array() const { return false; }
+    virtual bool is_boolean() const { return false; }
     virtual bool is_date() const { return false; }
     virtual bool is_error() const { return false; }
     virtual bool is_function() const { return false; }