[v3] Add prerequisites 5/6

> ⚠️ If you have issues / are unsure, create ONE PR PER EXERCISE so it's easier to merge them as we can have discussions per exercise. If you're certain, it's fine to do a single one.

The idea is to split #960 into smaller chunks.

Here is the list of practices exercises to deal with for this part :

```
bowling

strain

accumulate

flatten-array

nth-prime

sieve

rotational-cipher

diffie-hellman

affine-cipher

atbash-cipher

crypto-square

robot-simulator

kindergarten-garden

sum-of-multiples

change

point-mutations

protein-translation

armstrong-numbers

dnd-character

run-length-encoding
```