[web] introduce useStaffCanSee hook for web

Summary:
I want to introduce this hook to web so that we can gate some a new appearance settings for non staff members while the light mode/color families for web project is in progress

Depends on D9193

Test Plan: flow and confirmed that the correct value was being returned by hook (returns true during dev mode or when the user is a member of the staff array)

Reviewers: atul, rohan, inka

Reviewed By: rohan

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9194