More lessons for programmers (braces, brackets, more symbols...)

Hi! Thanks for your hard work! Love that you included lessons for numbers and some symbols.

This came out a while back: https://news.ycombinator.com/item?id=9577799

One of the most frequently requested features for it was more lessons for programmers, we don't usually type long essays :) But it's hard to tell if its author wants to make any improvements. Perhaps you can?
