I've added a couple of paragraphs under a new H2 for _Publishing a plugin to the library_ to help with #4673 .

Instead of just adding a tiny note on how much time Algolia would take to add the page to the library, based on my previous experience, I thought it was best to create a new section on publishing as it could be a bit confusing for beginners (in the very least, it was for me). The wording is still probably a bit off, feel free to suggest changes 😄 

**PS:** In the first section of this page we say we'll review "what a plugin is _not_", but I don't this in any explicit way here... what was your line of thought in including this?