Updated description of Event to reference historical events.

[RichardWallis]

Also added historical event example.

Implements issue #1931.

[danbri]

I want to take a look into this topic a bit first, if that's alright...

[smrgeoinfo]

While you're editing the definition ... currently we have suggested "Event: An event happening at a certain time, past or future, and location..." Please can we have a non-circular definition? Is there such a thing as an event that does not happen at a certain time and location? Basically the current definition boils down to 'an event is an event'.

How about something like:
Event:
"Something that occurs in a certain place during a particular interval of time" (https://www.dictionary.com/browse/event);
"an occurrence; something that happens" (https://wikidiff.com/event/process, https://www.merriam-webster.com/dictionary/event).

[github-actions]

This pull request is being tagged as Stale due to inactivity.

[RichardWallis]

@danbri can we revisit this - note recent activity in #503