Kata

Write a class that, when given a string, will return an uppercase string with each letter shifted forward in the alphabet by however many spots the cipher was initialized to.

For example:

var c = new CaesarCipher(5); // creates a CipherHelper with a shift of five
c.encode('Codewars'); // returns 'HTIJBFWX'
c.decode('BFKKQJX'); // returns 'WAFFLES'

c = new CaesarCipher(5) # creates a CipherHelper with a shift of five
c.encode('Codewars') # returns 'HTIJBFWX'
c.decode('BFKKQJX') # returns 'WAFFLES'

c = CaesarCipher(5); # creates a CipherHelper with a shift of five
c.encode('Codewars') # returns 'HTIJBFWX'
c.decode('BFKKQJX') # returns 'WAFFLES'

c = CaesarCipher.new(5); # creates a CipherHelper with a shift of five
c.encode('Codewars') # returns 'HTIJBFWX'
c.decode('BFKKQJX') # returns 'WAFFLES'

$c = new CaesarCipher(5);
$c->encode('Codewars'); // returns 'HTIJBFWX'
$c->decode('BFKKQJX'); // returns 'WAFFLES'

let c = CaesarCipher::new(5);
c.encode("Codewars"); // returns "HTIJBFWX"
c.decode("BFKKQJX"); // returns "WAFFLES"

If something in the string is not in the alphabet (e.g. punctuation, spaces), simply leave it as is.
The shift will always be in range of [1, 26].