Add tests to Math (#423)

* Add prettier config

* test: add test to check for absolute function

* chore: es5 to es6

* test: add test to check mean function

* test: add test for sum of digit

* test: add test for factorial

* test: add test for fibonnaci

* test: add test for find HCF

* test: add test for lcm

* test: add gridget test

* test: add test for mean square error

* test: add test for modular binary exponentiation

* test: add tests for palindrome

* test: add test for pascals triangle

* test: add tests for polynomial

* test: add tests for prime check

* test: add tests for reverse polish notation

* test: add tests for sieve of eratosthenes

* test: add tests for pi estimation monte carlo method

* chore: move tests to test folder

* chore: fix standardjs errors

Maths/DigitSum.js

@@ -0,0 +1,16 @@
+// program to find sum of digits of a number
+
+// function which would calculate sum and return it
+const digitSum = (num) => {
+  // sum will store sum of digits of a number
+  let sum = 0
+  // while will run untill num become 0
+  while (num) {
+    sum += num % 10
+    num = parseInt(num / 10)
+  }
+
+  return sum
+}
+
+export { digitSum }