Add 2D triangulation plot

It would be very useful for me adding a new chart type to deal with 2D triangulation (or mesh).

At the current implementation, I found different workarounds but with some limitations:

• the heatmap graph is only for data in grid format
• the mesh3d graph shows three dimensions and it manages also the lights, resulting for my purpose too complex (and expensive)
• the basic scatter plot allows me to draw a single triangle, but if I try for many triangles (>10k) the function is extremely expensive.

I apologize in advance if this feature is already implemented and I missed it.

まず、既存の heatmap、mesh3d、scatter チャートの実装を確認し、それらのデータとレンダリングに関する制限を理解します。新しいチャートタイプを提案する前に、2D 三角形分割またはメッシュの想定入力、レンダリング動作、および大量の三角形に対するパフォーマンス目標を定義します。