Adds calendso to Booking and Scheduling (#2502)

Co-authored-by: Prayash Mohapatra <424487+prayashm@users.noreply.github.com>

README.md

@@ -1314,6 +1314,7 @@ _See also [Monitoring](#monitoring)_
 ### Booking and Scheduling
 
 - [Alf.io](https://alf.io/) - The open source ticket reservation system. ([Demo](https://demo.alf.io/authentication), [Source Code](https://github.com/alfio-event/alf.io)) `GPL-3.0` `Java`
+- [Calendso](https://calendso.com/) - The open-source online appointment scheduling system. ([Demo](https://app.calendso.com/bailey), [Source Code](https://github.com/calendso/calendso)) `MIT` `Nodejs`
 - [Easy!Appointments](http://easyappointments.org/) - A highly customizable web application that allows your customers to book appointments with you via the web. ([Demo](http://easyappointments.org/demo/), [Source Code](https://github.com/alextselegidis/easyappointments)) `GPL-3.0` `PHP`
 
 ## Proxy