[FR] Allow Creating Simple Slideshows

### Description

It would be really nice to be able to create slideshows in Appflowy using markdown syntax. Obsidian allows creating simple slideshows and separating slides using three dashes (---) on a line as the seperater, and that has always been helpful to quickly create slideshows from my notes that look nice and aren't super complicated. It wouldn't have to support complex slideshows or lots of extra slideshow features, but just having something to display a few lines of text and some pictures for a quick and easy presentation would be nice. Perhaps it could be implemented by integrating something like SuperDeck: https://github.com/leoafarias/superdeck. (P.S. I haven't looked into SuperDeck much or whether it would be feasible to actually use it, it's just an idea for what slideshows in AppFlowy could look like).

### Impact

This feature would be useful for people who have project plans and notes in AppFlowy and want a simple way to present their project without having to copy their notes into a different application. It would also be nice for teams who use AppFlowy to see and make presentations together without having to use a different application.

### Additional Context

_No response_