support inject extra class names to widget

I want to add extra class name to the field widget them use css style that field, for example

    attributes: [
        {
            code: 'name',
            label: 'Name',
            type: 'string',
            extraClass: 'short',
        },
    ]

then we get html

    <div data-dojo-attach-point="containerNode">
        <div id="gform_group_DecoratorWidget_7" class="editor row Decorator short" widgetid="gform_group_DecoratorWidget_7">
    </div>

With the help the extra class name, we can change some short field(like string) to `inline-block` to save page room, and keep long field(like richtext) to `block`

    .editor.row.Decorator.short {
        display: inline-block;
        margin-right: 14px;
    }

Not sure if the good place to add the code, at least it work, :smile: