Add an option to share exercises to calistree users and non-users with a link.

Users can easily see the exercise in the app with the link and add them in their session. Non-users would see a banner to join calistree OR a mini-webpage kind of thing to see the exercise as a demo kind (if doable).

This would add to the functionality and accessibility to the app. I find myself wanting to show someone a particular exercise but I have to tell them to search it. It would be great to add an option to share exercises and also it acts as a promotional item. As a satisfied user I want this app to grow. Thank you.