comment profinite example

[kbuzzard]

I've added a lot of comments for the profinite example Lean file. My personal opinion from having watched students is that there are two kinds. There are those that don't read any of the documentation whether it be on a web page or in the file, and just start playing about. And there are those that want to carefully read docs and play with Lean at the same time, and for those people it's really annoying when the docs are on another page. I always put many many comments in my teaching material now, I think students find it easier, and VS Code makes it very clear what is a comment and what isn't.

Obviously other people's views might differ; I don't think I'm going to plough through the other three example lean files until I've heard people's thoughts on this PR and #120.

[adamtopaz]

I guess one question we need to answer is who the intended audience for these files actually is. My original intention was for these to be read by mathematicians who were already very familiar with the mathematics, so I saw the docs more as hints for how to translate the math into Lean's type theory.

But I do agree that more detail probably won't hurt!

Let see what others think...