[Bug] Legend 'xanchor' setting plot's x position rather than legend's

[wunderBarr7]

When using horizontal legend orientation, using the 'xanchor' property sets the plot's x position rather than the legend's x position.

Link to Example Code

[OpportunityLiu]

You'd set x: 0.5 with xanchor: 'center' to center the legend.

legend: {
    orientation: 'h',
    xanchor: 'center',
    x: 0.5,
  }

The default value of x is 0, with xanchor: 'center', the legend will be aligned with 0 at its center.