Video player example

## 🚀 Feature

A video player example.

## Motivation & Examples

Many common uses of social meta apps watch a video file.

Implement a demo demonstrating video playback on all platforms.

The video stream example also completes this partially from a device, but not from a file.

I may be able to work on this if there is a sketch of an approach to video playback.

Start by locating the existing video stream example and reviewing how it handles playback from a device rather than a file. Define an approach for file-based video playback across all supported platforms, then verify that the completed demo works on each platform.

Written by the indexing model from the issue text.