__AddConfigAdds a config key and config value to the Element object.
| Key | Description | 
|---|---|
| element | Any Element object. | 
| type | A case-sensitive string representing the config key. | 
| value | The config value, which can be of any type. | 
Developers can set some custom configs for the Element to facilitate extensions by the frontend framework.
No return value.
The frontend framework can generate render directives in the following way.