"captions" node in the configuration

[stockiNail]

As done by PR #51, I think it could be helpful to configure also the captions.

This is how the config will look like:

  captions: {
    align: undefined,
    color: undefined,
    display: false,
    formatter: (ctx) => ctx.raw.g,
    font: {},
    padding: 3
  },

The options groupLabels should be removed in favor to captions.display .
I have already implemented in my fork and I'm testing it.
Let me know if makes sense.

[stockiNail]

In my implementation, I have removed the formatter and the label can show only the group name.

TreemapElement.defaults = {
  borderSkipped: undefined,
  borderWidth: undefined,
  dividerCapStyle: 'butt',
  dividerColor: 'black',
  dividerDash: undefined,
  dividerDashOffset: 0,
  dividerWidth: 0,
  groupDividers: false,
  spacing: undefined,
  label: undefined,
  rtl: undefined,
  captions: {
    align: undefined,
    color: undefined,
    display: true,
    font: {},
    padding: 3
  },
  labels: {
    align: 'center',
    color: undefined,
    display: false,
    formatter: (ctx) => ctx.raw.g ? [ctx.raw.g, ctx.raw.v] : ctx.raw.v,
    font: {},
    position: 'middle',
    padding: 3
  }
};

[kurkle]

Looks good, I'd be happy to review a PR for that!

[stockiNail]

Looks good, I'd be happy to review a PR for that!

Fine! Let me finish that PR #51 (I'm working on the documentation, hoping to commit it soon), because this PR is implemented basing on the other.

[stockiNail]

Looks good, I'd be happy to review a PR for that!

PR #54 submitted. Doc is missing but coming soon (if PR is ok)