Add information about single lesson

Author: bkmgit

_config.yml

@@ -75,7 +75,8 @@ title: "Workshop Title"
 
 # This setting (kind) takes configurations from the styles
 # template. Please do not modify this. If you are teaching 
-# a custom set of lessons, use a custom schedule.
+# a custom set of lessons or a single lesson, use a custom 
+# schedule.
 kind: "workshop"
 
 # Magic to make URLs resolve both locally and on GitHub.