Add ROT13 cipher (#463)

* Add ROT13 cipher

* Update ROT13.js

Co-authored-by: Sutthinart Khunvadhana <sutthinart.khunvadhana@refinitiv.com>
Co-authored-by: vinayak <itssvinayak@gmail.com>

Ciphers/ROT13.js

@@ -0,0 +1,21 @@
+/**
+ * Transcipher a ROT13 cipher
+ * @param  {String} text - string to be encrypted
+ * @return {String} - decrypted string
+ */
+const transcipher = (text) => {
+  const originalCharacterList = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
+  const toBeMappedCharaterList = 'NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm'
+  const index = x => originalCharacterList.indexOf(x)
+  const replace = x => index(x) > -1 ? toBeMappedCharaterList[index(x)] : x
+  return text.split('').map(replace).join('')
+}
+
+(() => {
+  const messageToBeEncrypted = 'The quick brown fox jumps over the lazy dog'
+  console.log(`Original Text = "${messageToBeEncrypted}"`)
+  const rot13CipheredText = transcipher(messageToBeEncrypted)
+  console.log(`Ciphered Text = "${rot13CipheredText}"`)
+  const rot13DecipheredText = transcipher(rot13CipheredText)
+  console.log(`Deciphered Text = "${rot13DecipheredText}"`)
+})()