Update Plots.jl's colorbar_titel maps to PGFPlotsX's `color bar sty…

…le={ylabel}` (#3848)

* Update PGFPlotsX colorbar_titel map to ylabel

For most of the backends supported by Polts.jl the `colorbar_title` attribute maps to the attribute in the backend that ultimately is displayed on the vertical axis of the colorbar, which is vertically aligned. Not for PGFPlotsX as in this backend the `title` attribute is displayed on top of the colorbar while the `ylabel` is shown on the vertical bar.

* Update .zenodo.json

added my name to the contributors list

.zenodo.json

@@ -692,6 +692,10 @@
         {
             "name": "Fred Callaway",
             "type": "Other"
+        },
+        {
+            "name": "Jan Thorben Schneider",
+            "type": "Other"
         }
     ],
     "upload_type": "software"

src/backends/pgfplotsx.jl

@@ -203,7 +203,7 @@ function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
 
             if hascolorbar(sp)
                 cticks = get_colorbar_ticks(sp)[2]
-                colorbar_style = PGFPlotsX.Options("title" => sp[:colorbar_title])
+                colorbar_style = PGFPlotsX.Options("ylabel" => sp[:colorbar_title])
                 if sp[:colorbar] === :top
                     push!(
                         colorbar_style,