Configs can hold simple instance properties.

<pre class="runnable readonly text">
class Simple extends Base {
    static config = {
        className: 'Demo.view.component.Simple',
        ntype: 'demo-simple-component',

        foo: 1, // An instance field

    }
}
...
items: [{
    module: Simple

    header: {iconCls: 'fa fa-home', text: 'Simple'},

}, {
    module: Simple
    foo: 2, // This value is used for the instance

    header: {iconCls: 'fa fa-home', text: 'Simple'},
}],
</pre>
