Datalabels plugin support

[myungsunscott]

Your issue description

Hi, it's a great addon for Vaadin. Appreciate all the work you've put into this.

Just wondering if you'd consider adding support for the chartjs datalabels plugin?

https://chartjs-plugin-datalabels.netlify.app/ or this one https://emn178.github.io/chartjs-plugin-labels/samples/demo/

It would add a lot of really nice functionality to the existing charts. Thanks again!

Your configuration

Vaadin 8

Your screenshots