Added OnClick for charts

[yannikHoeflich]

This PR adds an OnClick attribute for all charts here is an example for a pie chart:

<PieChart  @ref="pieChart" Width="500" OnClick="Clicked" />

@code{
    // Other stuff

    private void Clicked(string labelName){
        Console.WriteLine($"Clicked on: ${labelName}");
    }
}

The parameter for the event is the label name, sadly there is not really a better option.

[yannikHoeflich]

I updated it to use the new ChartClickArgs. Now you can get the label name and index. So now it looks more like this:

<PieChart  @ref="pieChart" Width="500" OnClick="Clicked" />

@code{
    // Other stuff

    private void Clicked(ChartClickArgs args){
        Console.WriteLine($"Clicked on: {args.LabelName} with index {args.Index}");
    }
}

[gvreddy04]

@yannikHoeflich Thank you for your time and the pull request. I'll take care of it.