Display upcoming and past events

Created by: flora8984461

I am creating a separate branch since I want to compare with #109 (Cuz for this branch I am having an annoying warning, the functions are all working fine, but I still wanna see if I can fix it...)

---------Update-2020-10-01-----------------------

• Checkbox "Include past events"-By default, show upcoming events, if include past events, after upcoming events finished loading, show past events
• greyscale past events, and also include a header as a separation that says: Past Events before we list all the past events.
• remove the Unknown "Event type"

NOTE:

• Fix the warning Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.

Signed-off-by: Yi Liu yi.liu@eclipse-foundation.org