Centralized Calendar General and End User Documentation

[alexanderl19]

On the centralized-calendar branch, I have created stub files for overview and the end user guide.

The overview is just meant to give general details about the project to someone unfamiliar, and direct users to the correct areas of documentation.

The end user guide is a separate page we will mainly use for guiding members of other clubs through locating and sending us their calendar link. This page should also cover any relevant details on how events should be formatted.