This element tag is used to invoke an action of any selectors that has ref
attribute within custom element. Only live inside a <element-flow>
<custom-element name="my-element">
<element-state name="content" type="string"></element-state>
<element-flow>
<trigger-event input="Input">
<set-state name="content" value="$.target.value" from="event"></set-state>
</trigger-event>
</element-flow>
<template>
<input ref="Input" type="text" />
<div>
Content:
<slot name="#content"></slot>
</div>
</template>
</custom-element>
<my-element></my-element>