add modal functinality to calendar page

[QueMona98]

Bootstrap should already be installed in the project. Use the following link:

https://react-bootstrap.github.io/components/modal/

This link outlines how to use the modal provided by bootstrap. The goal is to give users the option to click a date on the calendar and cause a modal to pop up that would allow the user to see all the details of the events taking place that day. They should then have an option to close the modal or sign up for any of the events on the modal.