Add ImageExport renderer for playwright-dotnet

Description

As plotly.js, the underlying library that Plotly.NET is using needs an environment that can execute javascript to render images programmatically.

https://github.com/microsoft/playwright-dotnet seems to be another stable, mature option for automating tasks on a headless browser.

Pointers

• A reference implementation for this using PuppeteerSharp can be seen here

首先閱讀 src/Plotly.NET.ImageExport/PuppeteerSharpRenderer.fs，這是影像匯出的參考實作。在研究 playwright-dotnet API 之前，使用它來了解預期的 renderer 結構。完成的標準是：playwright-dotnet 有可用的同等 ImageExport renderer，且現有的影像匯出行為仍受到支援。