Updated README for comboboxes page (#1704) (#1754)

Author: greuelpirat

README.md

@@ -72,6 +72,8 @@ To load the source project you will need Visual Studio 2019. Don't worry if you
 
 ![Alt text](web/images/screen-fields.png "Fields")
 
+![Alt text](web/images/screen-comboboxes.png "ComboBoxes")
+
 ![Alt text](web/images/screen-palette.png "Palette")
 
 ![Alt text](web/images/screen-colortools.png "Color Tools")