Add "PROMPT SHELFS" to the PROMPT LIBRARY

In your great prompt library, add "Prompt Shelf" categories to the library + add a management feature to allow/prevent access to "prompt shelf" by users.

This would be useful to prevent users from accessing prompts that are on shelfs they are not supposed to have access to (internal prompts versus public prompts, admin prompts versus user prompts, etc…).

Also good to not overwhelm users with a prompt library they have no clue about.