assistant: Add `/now` slash command (#12856)

This PR adds a `/now` command to the Assistant for indicating the
current date and time to the model.

Release Notes:

- Added `/now` command to the Assistant for getting the current date and
time.
0d5485bd6cMarshall Bowers committed on 6/10/2024, 6:05:02 PM· committed by GitHubparenta600799
3 files changedLine totals unavailable