Separate into core and express packages

Just as the python lib, Plotly.NET provides both low-level access to plotly.js figure generation (e.g.TraceStyle functions, Chart.Scatter) and high-level abstractions for composite charts (e.g. Chart.Grid, Chart.Range).

Once a full low-level coverage is reached on 2.x.x, it might be beneficial to split these layers to both make the chart namespace more concise and add dependencies such as a data frame library to the high level abstractions.

此 issue 未指定特定的檔案或測試。先檢視專案與 package 的配置，接著檢查 Chart 命名空間，以及低階的 TraceStyle 和 Chart.Scatter API，同時檢視高階的 Chart.Grid 和 Chart.Range 抽象。要視為完成，需要定義拆分為 core 與 express package，但所需的涵蓋範圍與相依性邊界仍有待釐清。