fix: update lesson to reflect changes in UI and in number of the repos (#1108)

Fixes #981. When updating the
text I found out the examples don't work anymore, so I updated them too.
I also changed some bits of code and texts, hopefully for the better.

I only touched the first half of the lesson which deals with Facebook, I
didn't dare to even look further not to make this PR even larger. This
was supposed to be a small fix, but ended up as pretty much a rewrite.
Unfortunately that's something which I suspect will be true for most of
the issues labeled as Academy 😬

Asking @TC-MO to review the text, and guessing that @metalwarrior665 🤘
could be the best person to review the code examples.

Author: honzajavorek