merge: Optimize the space complexity of the fibonacci algo (#899)

* docs: update js doc

* feat: add number type validation condition

* pref: Optimize space complexity

remove the Array from the algo and used two flag varible to calculate last two numbers & optimize the sapce complexity O(n) to O(1)

* test: add test case for invalid types

Dynamic-Programming/tests/FibonacciNumber.test.js

@@ -1,6 +1,12 @@
 import { fibonacci } from '../FibonacciNumber'
 
-describe('FibonacciNumber', () => {
+describe('Testing FibonacciNumber', () => {
+  it('Testing for invalid type', () => {
+    expect(() => fibonacci('0')).toThrowError()
+    expect(() => fibonacci('12')).toThrowError()
+    expect(() => fibonacci(true)).toThrowError()
+  })
+
   it('fibonacci of 0', () => {
     expect(fibonacci(0)).toBe(0)
   })