Add more exercises

[FedericoCeratto]

Workrave provides a set of exercises for general health that could be reused in SafeEyes without any licensing issue: https://github.com/rcaelers/workrave/tree/main/ui/data

Related to #439

[archisman-panigrahi]

@FedericoCeratto Can you please write down some suggested exercises in comments in this thread?

[FedericoCeratto]

They are listed here https://github.com/rcaelers/workrave/blob/main/ui/data/exercises/exercises.xml.in and have pictures to clarify the movements. I would suggest reaching out to the author or maybe even have workrave and safeeyes be able to work together.