[camera_web] Support camera image streams on the web

[aalex]

Implement image camera streams on the web.

Use case

It would be useful to add support for the streaming images with the camera plugin on the web. It would allow developers to implement all kinds of use cases, including computer vision, saving images and much more.

Proposal

Add support for the streaming images with the camera plugin on the web

Example

Here is an example of how to initialize the image stream of a camera controller:

    controller = CameraController(cameras[0], ResolutionPreset.medium);
    controller.initialize().then((_) {
      if (!mounted) {
        return;
      }
      controller.startImageStream((CameraImage availableImage) {
        // Process each image here.
      });
    });

See also

• Camera document how to use ImageStream #26348 for the ticket about the documentation for this image stream API.