Add Chat example

[terrysahaidak]

This PR implements a very naїve chat interface that renders fully on UI-thread using Skia imperative canvas API.

The goal of this example is to help debug some of the problems that we face when developing complex applications with imperative API.

Features:

• offscreen rendering
• onscreen rendering using skia context + webgpu canvas
• rasterizing each message (rendering offscreen into textures)
• dynamic background (changes based on scroll offset)
• rendering only visible messages
• update canvas texture only when something has changed

Example

2024-11-20.16.56.54.mov