Being stuck at home, bored, desperate and coming up with a lot of weird ideas, a friend asks you to develop a tool to measure his ocular skills: one of those [Monoyer charts](https://en.wikipedia.org/wiki/Monoyer_chart) that ophthalmologists use.
Generate a board where each new letter is harder, bigger, bolder and stronger!
Write the function `generateLetters` which creates 100 `div`, each containing a letter randomly picked through the alphabet, and whose style properties have to be increased: