Add 3 new encryption methods to Giveaways Encrypter/Decrypter

[rafaelgomesxyz]

Current method is: rotate each character in the code using rot13 and convert it to hexadecimal using its ASCII code.

Add 3 new methods:

1. Same as current method, but convert each number in the encrypted code to an uppercase letter using a secret alphabet.
2. Same as current method, but using a random rotation number between 1 and 25 instead of the fixed number 13.
3. Same as current method, but combining both items above.

The method should be selected randomly.