Calendar event export

[maxime-killinger]

Currently, I'm working on a calendar export of the workouts. I don't know if you're interested in this type of pull request.
My objective is to be able to export every workouts in the selected calendar in settings, with all the informations that’s on the app.
It's look like something like these screenshots.

You can check on my dedicated branch event export

[piscoTech]

It's a nice feature. I feel many people would like something like this, please open a PR.