be-deslotted

Transfer values from light children to host.

<my-custom-element>
    #shadow
        <slot name=link be-deslotted=href></slot>
    <a slot=link href=//cnn.com>This is CNN</a>
</my-custom-element>

my-custom-element's href property gets set to //cnn.com

Props can be mapped via propMap. [TODO]: Show example.