Use colhz for ztitle

Author: linev

demo/examples.json

@@ -106,7 +106,7 @@
      { "opt": "chord", "title": "Chord diagram as it is implemented by d3.js, see https://observablehq.com/@d3/chord-diagram" },
      { "opt": "allbins", "title": "draw underflow/overflow bins" },
      { "name": "xyticks", "opt": "xticks:[-3.8,-1.5,1.5,3.8];yticks:[-3.3,-1.1,1.1,3.3]", "title": "configure custom x and y ticks positions" },
-     { "name": "ztitle", "opt": "colz;ztitle:Z^{axis}%20title;nostat", "title": "Color plot with custom Z title" },
+     { "name": "ztitle", "opt": "colhz;ztitle:Z^{axis}%20title;nostat", "title": "Color plot with custom Z title" },
      { "name": "pol", "opt": "lego2;pol", "title": "Polar coordinates for lego plots" },
      { "name": "cyl", "opt": "lego2;cyl", "title": "Cylindrical coordinates for lego plots" },
      { "name": "sph", "opt": "lego2;sph", "title": "Sphere coordinates for lego plots" },