add example for empty buttons

example/controldeck.conf

@@ -6,7 +6,7 @@
 # color-bg = hex color code
 #
 #  : N.        optional number to specify group/row
-#  : NAME      name of the button
+#  : NAME      id, name of the button
 #  : name      sink name, see name with either:
 #                pactl list sinks short
 #                pamixer --list-sinks
@@ -22,11 +22,16 @@
 # icon = Font Awesome name
 #
 #  : N.        optional group/row specification
-#  : NAME      name of the button
+#  : NAME      id, name of the button
 #  : color-bg  background color
 #  : color-bg  forground color
 #  : command   command(s) to run
 #  : icon      use icon instead of NAME (Font Awesome), e.g.: fas fa-play
+#
+# [N.empty.NAME]
+#
+#  : N.        optional number to specify group/row
+#  : NAME      id, name of the button
 
 [gui]
 width = 800