merge: Add Affine Cipher (#1067)

* Add Affine Cipher

* Replace IndexOf function to improve performance

* remove leading spacing and fixed typo

* Remove leading spacing in first row.

Ciphers/test/AffineCipher.test.js

@@ -0,0 +1,27 @@
+import { encrypt, decrypt } from '../AffineCipher'
+
+describe('Test Affine Cipher', () => {
+  it('Test - 1, Pass invalid input to encrypt function', () => {
+    expect(() => encrypt(null, null, null)).toThrow()
+    expect(() => encrypt('null', null, null)).toThrow()
+    expect(() => encrypt('null', 1, null)).toThrow()
+    expect(() => encrypt('null', null, 1)).toThrow()
+  })
+
+  it('Test - 2, Pass invalid input to decrypt function', () => {
+    expect(() => decrypt(null, null, null)).toThrow()
+    expect(() => decrypt('null', null, null)).toThrow()
+    expect(() => decrypt('null', 1, null)).toThrow()
+    expect(() => decrypt('null', null, 1)).toThrow()
+  })
+
+  it('Test - 3 Pass string value to encrypt and ecrypt function', () => {
+    const a = 5
+    const b = 8
+    expect(decrypt(encrypt('HELLO WORLD', a, b), a, b)).toBe('HELLO WORLD')
+    expect(decrypt(encrypt('ABC DEF', a, b), a, b)).toBe('ABC DEF')
+    expect(decrypt(encrypt('Brown fox jump over the fence', a, b), a, b)).toBe(
+      'BROWN FOX JUMP OVER THE FENCE'
+    )
+  })
+})