message: fix(Chart): expose type coercion functions for charts
diff: - [Inject the needed libraries](#inject-the-needed-libraries)
  - [Set up the chart](#set-up-the-chart)
  - [Supported chart types](#supported-chart-types)
  + - [Chart Type Coercion](#chart-type-coercion)
  - [AmCharts documentation](#amcharts-documentation)
  <!-- END doctoc generated TOC please keep comment here to allow auto update -->
  @@ -81,13 +82,34 @@ setUpChart(chart: am4charts.Chart) {
  - `pie`
  - `map`
  - `radar`
  -- `treemap`
  +- `tree`
  - `sankey`
  - `chord`
  > See `TsChartVisualizationOptions` for all supported types.
  +### Chart Type Coercion
  +
  +The library exposes functions for coercing to specific chart types:
  +
  +- `tsChartXYTypeCheck`
  +- `tsChartPieTypeCheck`
  +- `tsChartMapTypeCheck`
  +- `tsChartRadarTypeCheck`
  +- `tsChartTreeTypeCheck`
  +- `tsChartSankeyTypeCheck`
  +- `tsChartChordTypeCheck`
  +
  +Example:
  +
  +```typescript
  +if (tsChartXYTypeCheck(chart)) {
  + // Now we know we are dealing with an XY chart type
  +}
  +```
  +
  +
  ## AmCharts documentation
  See https://www.amcharts.com/docs/v4/ for full documentation.
  