Expose attributes and events of inner elements

[seanchas116]

Description

Expose attributes and events of inner elements

(For forms etc)

Example (React)

<my-form name--value={name} onname--change={setName} onsubmit--click={submit} />

https://codesandbox.io/s/sweet-sound-8goyrf?file=/src/App.tsx

(React 19 will support decrative syntax for subscribing custom element events)