[gvreddy04]

Chart.js options that take a JavaScript function can now be set from C#. The app registers each function by name in its own JavaScript file, and C# references it with ChartFunction. Only registered functions resolve: a name is never evaluated as code, and globals such as window.open or fetch can't be reached by name.

• blazorexpress.chartjs.registerFunction(name, fn) registers a function; new ChartFunction("name") references it. References are resolved on create, on every update and when a dataset is added.
• An unregistered name logs one console error naming the function and the option, and the option keeps its Chart.js default. A function that throws is logged once and the chart keeps drawing.
• Function options: ChartAxesTicks.Callback; the 14 tooltip callbacks, External, Filter and ItemSort; legend OnClick, OnHover, OnLeave and labels Filter, Sort and GenerateLabels; datalabels Formatter, chart-wide and per dataset; ChartAnimation.OnProgress and OnComplete; ChartOptions OnClick, OnHover and OnResize.
• A legend OnClick function replaces Chart.js's default toggle, as in Chart.js. The library still keeps the visibility the click changed across UpdateAsync and still raises OnLegendClick.
• Colour properties on every dataset gain a ...Function sibling (for example BackgroundColorFunction), sent instead of the value when set; line and radar also get point colour functions. A function can return a canvas gradient.
• LineChartDataset.SegmentStyle (ChartLineSegment) styles line segments with values or functions; Segment stays as it is.
• ChartAxesTicks.Format (ChartNumberFormat) formats linear, logarithmic and radial axis labels as currency, percent or compact numbers with no JavaScript. The tooltip value uses the same format.
• The library's datalabels background now works with a function colour.
• Existing properties, defaults and their JSON are unchanged.

Adds six demos (currency ticks, tick and tooltip functions, legend filter, legend click function, segment styling, gradient fill), a "JavaScript functions" getting-started section, docs tables, an unlisted /demos/js-functions-self-check page that checks 44 cases on live charts, and JSON tests.