Add Freva Workshop 2024 presentation to Talks

[felio92]

I added the presentation for the Freva Workshop of this year to the repo. I split the presentation into two parts, one for each day of the workshop. The index.slides.html page in the Freva_Workshop_2024 folder contains links to both of the presentations, so navigating to the respective presentation would go like this:

[eelucio]

lgtm!