feat: support Frappe Charts charting library

[jooyoungseo]

Summary

Add support for Frappe Charts as a third-party charting library that maidr can work with.

Background

Frappe Charts is a lightweight, open-source SVG charting library with zero dependencies, inspired by GitHub's contribution chart. It is popular for its simplicity and clean API. chart2music provides a Frappe Charts integration example.

What This Involves

• Binder/Adapter: Create an adapter that extracts data from Frappe Charts instances and generates the MAIDR JSON schema.
• SVG Highlighting: Frappe Charts renders standard SVG elements, making CSS selector-based highlighting straightforward.
• Chart Types: Frappe Charts supports line, bar, mixed (axis), scatter (dot), pie, percentage, and heatmap charts.

Considerations

• Frappe Charts has a simple, well-documented API making data extraction straightforward.
• chart2music notes that Frappe Charts does not fully support external visual syncing via its API.
• The library is lightweight and has minimal chart types, so the integration scope is smaller than libraries like D3 or Highcharts.

Reference

• chart2music Frappe Charts example: https://codepen.io/chart2music/full/QWmrWWE
• Frappe Charts: https://frappe.io/charts