add AI Hub: AI Agent, AI Function, AI Task

The most powerful AI agent feature now is live in UChat.

Check the help docs:
https://uchat.atlassian.net/wiki/spaces/UKB/pages/1028653059/AI+Hub

Check the youtube playlist here:
https://www.youtube.com/playlist?list=PLYV-IhQ_GwTN_jRy7jqhvpwvpWDac4EZY