* In a few words, a Decorator is a Component that wraps around another Component. A typical example of a Decorator is a* A Decorator can be thought of as a lightweight Container that has only one child item, and no layout overhead.* Another powerful feature that Decorator provides is config proxying. For example: all config items of a* and a waste of code space. Instead, when you sub-class Ext.Decorator, all you need to do is to specify those config items* that you want to proxy to the Component using a special 'proxyConfig' class property. Here's how it may look like* Once `My.field.Slider` class is created, it will have all setters and getters methods for all items listed in `proxyConfig`* automatically generated. These methods all proxy to the same method names that exist within the Component instance.