2023-3: Caesar Salad

A Caesar cipher, also known as a shift cipher, is one of the simplest encryption techniques.

In a Caesar cipher, each letter in the plaintext is replaced by a letter some fixed number of positions away in the alphabet, effectively "shifting" the alphabet.

Write code that:

- takes a character vector second argument representing the plaintext message

- takes a single integer first argument representing the size of the shift

- returns a result with the same shape as the second argument representing the encrypted message

The input will be uppercase letters and spaces.