doc(#41): document the new slot "info" to the code template

Author: peterpeterparker

doc/slides/slides.md

@@ -548,6 +548,8 @@ You could provide a file URI to the code you want to display or provide it with
 
 The slots `title` and `code` are optional.
 
+This template also exposes a slot `info` which would let you display an information over your code on mobile devices, useful to explain your reader that they should click to switch between vertical and horizontal scrolling. Find an example of the use of that slot on the [DeckDeckGo] website.
+
 ##### Notes
 
 Optionally a slot `notes` could be use to add some notes regarding the particular slide. These will be automatically `displayed` in the [remote control](https://deckdeckgo.app).