merge: Improved ciphers (#954)

* feat: imporved algorithm via replace method

* test: added two test cases

Ciphers/test/Atbash.test.js

@@ -0,0 +1,17 @@
+import Atbash from '../Atbash'
+
+describe('Testing Atbash function', () => {
+  it('Test - 1, passing the non-string as an argument', () => {
+    expect(() => Atbash(0x345)).toThrow()
+    expect(() => Atbash(123)).toThrow()
+    expect(() => Atbash(123n)).toThrow()
+    expect(() => Atbash(false)).toThrow()
+    expect(() => Atbash({})).toThrow()
+    expect(() => Atbash([])).toThrow()
+  })
+
+  it('Test - 2, passing all alphabets', () => {
+    expect(Atbash('HELLO WORLD')).toBe('SVOOL DLIOW')
+    expect(Atbash('The quick brown fox jumps over the lazy dog')).toBe('Gsv jfrxp yildm ulc qfnkh levi gsv ozab wlt')
+  })
+})