Added center text

[coderReview]

[emn178]

PieceLabel sound not related to this feature. it seems can be an independent plugin. something like

{
  pieceLabel: {
    // ...
  },
  centerLabel: {
    // ...
  }
}

You can create a new github project or just add into this project if you want to.

[coderReview]

Ok. Will do that. Thanks