Feature Request: Rendering specific slide in a ratio that is suitable for shared card image

Hi!

Following @gadenbuie advice I open this issue as a feature request:
Originally posted by @uriahf in https://github.com/gadenbuie/garrickadenbuie-com/discussions/115#discussioncomment-2954283

I want to render specific slides as an image for my social cards, @gadenbuie explained how to do it in his blog post but this solution works only for the first slide of the presentation.

I made a small workaround:
I created a new presentation that contains only the desired slide but with the ratio: 191:100 and then I used the code from the mentioned blog post:

https://github.com/uriahf/nb_step_by_step/blob/master/render_image_for_social_card.Rmd

It might be really useful to have a function for that :)

Start by reading the linked blog post and the workaround in render_image_for_social_card.Rmd to understand the current first-slide-only workflow and the 191:100 social-card ratio. Define the function's input and output behavior for selecting a specific slide, then verify that the selected slide renders at the requested ratio.