Add example 'next' alias to configuration

It shows the first todo item to be done, optionally with a filter
applied:

topydo next +Chores @Home

topydo.conf

@@ -49,6 +49,7 @@ append_parent_contexts      = 0
 
 [aliases]
 ;showall = ls -x
+;next = ls -n 1
 ;lsproj = lsprj
 ;listprj = lsprj
 ;listproj = lsprj