feat: add (string & import) remote src support

[luwes]

This PR adds support for creating a Mux clip from a remote source url.
A Next.js API is required in the web app to handle the /api/video route.

// pages/api/video/[[...handler]].ts
export { default } from '@mux/next-video/request-handler'

// app/page.tsx
import Video from '@mux/next-video';

export default function Home() {
  return <Video style={{ width: 640, aspectRatio: 2.4 }} src="https://stream.mux.com/A3VXy02VoUinw01pwyomEO3bHnG4P32xzV7u1j1FSzjNg/high.mp4" />;
}

saved in

// videos/https_stream.mux.com_A3VXy02VoUinw01pwyomEO3bHnG4P32xzV7u1j1FSzjNg_high.mp4.json
{
  "status":"ready",  
  "originalFilePath": "https://stream.mux.com/A3VXy02VoUinw01pwyomEO3bHnG4P32xzV7u1j1FSzjNg/high.mp4", 
  "externalIds":{"assetId":"0102502PiOVxFuSEdNESe7m00wrs00XBARJWZRBlFdTUcGxg","playbackId":"ohIr601A4CISlBV87dZZCfdL4yzvdgzlikajrvSjk8Hc"}, 
  "createdAt": 1695323804937, 
  "updatedAt": 1695323810259, 
  "blurDataURL": 
  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAOCAYAAABO3B6yAAAHWklEQVR4AQC..."
}

[heff]

Does the Readme need to change at all based on this?

Can you go ahead an update the readme as needed?

[luwes]

Will do, I'm still working out a bug where the JSON changes doesn't trigger a fast refresh (HMR)

[heff]

👍 Looks ok to me. I think we should get it in and then I'll do a more rigorous user test.