In "Single Choice Set" content type for instance - after you add 4 alternatives show info box informing the user that he has been added max number of alternatives for that question.
It should work like this:
User added alternative answer no 4.
Info message appears above "Add answer" button:
"You've added the maximum number of items."
"Add answer" button is disabled
User can dismiss this message on "X". "Add answer" button will still stay disabled
If user removes one of the alternatives - hide info message and enable "Add answer" button
Works the same for all other lists in the editor.
Use same "info" styling as we used here (the hub info msg): https://h5ptechnology.atlassian.net/browse/HFP-518
User should be informed there is a maximum number of list items.