Test and documents usage of Events triggered by revealjs

[cderv]

• General ones https://revealjs.com/events/
• For autoSlide behavior: https://revealjs.com/auto-slide/#events

Maybe this cold be used for some advanced behavior or widgets addition. 🤔

[cderv]

Seems like Reveal.on requires newer revealjs

[cderv]

Event can be triggered on slides using data-state https://revealjs.com/markup/#slide-states

This class will be applied on the viewport too