Refresh calendar after posting/approving event

[peterchinh]

Description
When an admin posts or approves an event, refresh the calendar to show the new event.

Acceptance Criteria
A clear and concise description of what you want to happen.

Steps:

• on calendar.tsx, add the new event on the calendar after posting an event as admin
• Do the same but when admin approves an event from the PendingApprovals modal (might need to a way to have this modal tell the calendar page it made a change)

Additional Information
The addEvent function may be useful since it gets passed into addEventPanel
Can also consider useSwr or any other caching alternatives