Dev: new dynamic widget for mcp app & Chinese website

[Chenglong-MS]

This pull request adds comprehensive Chinese-language development and extension guides for the Flint Chart project, updates chart documentation to clarify and expand property support, and improves the discoverability of the documentation. The most important changes are grouped below.

Update 1: Dynamic UI

We introduced improved dynamic UI for chart type exploration & property editing

Update 2: New Chinese websites

---

Details

New Chinese Documentation:

• Added docs/zh-CN/DEVELOPMENT.md as a full development guide, covering setup, repository structure, build/test commands, chart assembly pipeline, and extension points.
• Added docs/zh-CN/adding-a-backend.md, a step-by-step guide for implementing new rendering backends, including code structure, integration steps, and validation checklist.
• Added docs/zh-CN/adding-a-chart-template.md, detailing how to add new chart templates to an existing backend, with registration and testing instructions.
• Added docs/zh-CN/adding-a-semantic-type.md, explaining how to extend semantic types, register them, and ensure they are tested and documented.

Chart Properties and Documentation Updates:

• Updated agent-skills/flint-chart-author/SKILL.md to document new chart properties and clarify behaviors:
  • Added dodge property to "Grouped Bar Chart" and "Boxplot", and described its usage. [1] [2]
  • Clarified "Bar Chart" and "Stacked Bar Chart" usage for single vs. grouped series.
  • Improved documentation for "Violin Plot", "Pie Chart", and "Rose Chart", including new properties like sortSlices. [1] [2]
  • Added showTextLabels to "Waterfall" charts.
• Updated docs/reference-vegalite.md to remove the group encoding from "Bar Chart", reflecting the intended usage.

General Documentation Improvement:

• Added a link to the Chinese homepage in the main README.md for improved accessibility.