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.

[bbm-design]

tried your fork and got this error when trying the bar chart

Uncaught TypeError: can't access property "invokeMethodAsync", dotNetHelper is undefined
onClick http://localhost:5156/_content/Blazor.Bootstrap/blazor.bootstrap.js:1129
d http://localhost:5156/assets/plugins/global/plugins.bundle.js:46410
_handleEvent http://localhost:5156/assets/plugins/global/plugins.bundle.js:46416
_eventHandler http://localhost:5156/assets/plugins/global/plugins.bundle.js:46416
s http://localhost:5156/assets/plugins/global/plugins.bundle.js:46416
n http://localhost:5156/assets/plugins/global/plugins.bundle.js:46416
ct http://localhost:5156/assets/plugins/global/plugins.bundle.js:46410
ct http://localhost:5156/assets/plugins/global/plugins.bundle.js:46410

i have also seen that on multiple rows you have made reference to pie
even if the code concerns a different chart

example 

    window.blazorChart.bar.create(elementId, type, data, options, plugins);
    chart = window.blazorChart.pie.get(elementId);

[yannikHoeflich]

Sorry for the late response. I will take a look at it.

[yannikHoeflich]

Sorry, I forgot to do some changes at the other charts. That should fix it