A shift cipher takes a plain text message and shifts each letter forward in the alphabet by a given number.

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For example, a shift cipher with a shift of 1 would turn the string 'hello' to 'ifmmp'.
Create a class ShiftCipher that takes the numerical value of the shift as a constructor parameter. The class should have to methods:

• encrypt: takes a plain text string and returns a capitalized string with each letter shifted forward in the alphabet based on the set shift value.
• decrypt: takes and encrypted message and returns a lower case string with each letter shifted back in the alphabet based on the set shift value.
• In both methods, any character outside the alphabet should remain the same.
• But if a character is shifted outside the alphabet in either direction it should be wrapped around to the other side. For example, encripting a y with a shift of 4 results in C and decrypting an A with a shift of 1 result in z.
• Example:

const cipher = new ShiftCipher(2);
cipher.encrypt('I love to code!'); // returns 'K NQXG VQ EQFG!'
cipher.decrypt('K <3 OA RWRRA'); // returns 'i <3 my puppy'

Feel free to reference the Unicode Table as well as the JavaScript String methods including: toUpperCase(), toLowerCase(), charCodeAt() and fromCharCode()