[FEATURE] Display stack label for Stacked groups

Feature Proposal

When I use stacked groups, I want the possibility to display stack label if correct option is selected.

Suggestions of options:

this.chart = new Chart('canvas', {
      type: 'bar',
      data: {
        labels: this.barChartLabels,
        datasets: this.datasets;
      },
      options: {
        scales: {
          xAxes: [{
            display: true,
            stacked: barStacked,
            displayStackLabel: true
          }],
          yAxes: [{
            display: true,
            stacked: barStacked
          }],
        }
      }
    });

Feature Use Case

I have found a stack-overflow with exactly the same feature wanted : https://stackoverflow.com/questions/48643408/chart-js-grouped-sub-labels

[kpetrow]

This is actually resolved using datalabels plugin, and labels. Use labels as regular maybe adjusting vertical height to make room for datalabels. Also adjust datalabels vertical height and offset then use formatter

 chartSettings.options.plugins.datalabels.formatter = function (value, context) {
    let ds = context.chart.data.datasets
    // check if it's the first ds
    if (ds[context.datasetIndex - 1]) {
      // check if the ds is in the same stack as the ds before
      if (ds[context.datasetIndex - 1].stack == ds[context.datasetIndex].stack) {
        return ''
      } else {
        return ds[context.datasetIndex].stack;
      }
    } else {
      return ds[context.datasetIndex].stack;
    }

[firetunes]

+1 Would like this