Add axis title examples

Author: linev

demo/examples.json

@@ -44,6 +44,8 @@
      { "name": "xaxis_N", "opt": "xaxis_ff00ff", "title": "draw histogram X axis with color N - index or name like 'green' or hex like ff00ff" },
      { "name": "yaxis_N", "opt": "yaxis_00ff0055", "title": "draw histogram Y axis with color N - index or name like 'green' or hex like 00ff0055" },
      { "name": "htitle", "opt": "htitle:Custom%20histogram%20title", "title": "Change histogram title" },
+     { "name": "xtitle", "opt": "xtitle:Custom%20X%20axis%20title", "title": "Change X axis title" },
+     { "name": "ytitle", "opt": "ytitle:y_{axis}%20title", "title": "Change Y axis title" },
      { "opt": "inspect", "asurl": true, "file": "hsimple.root", "item": "hpx;1", "title": "universal object inspector, can be used for any class" },
      { "name": "docu", "file": "histpainter6.root", "layout": "vert32", "items": ["two_axis","draw_e1","draw_bar","draw_e34","draw_text"], "title":"several TH1 examples from THistPainter documentation" },
      { "name": "twoscales", "url": "nobrowser&file=$$$tutorials_hist.root&item=[twoscales/[1],twoscales/[3]]&opt=[hist,yaxis_red;line_red;y+]", "title": "interactive second Y scale to draw axis for second histogram" },
@@ -104,6 +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": "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" },