Added DegreeToRadian.js and DegreeToRadian.test.js in Maths directory

Maths/DegreeToRadian.js

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+/*
+ * Radian : https://en.wikipedia.org/wiki/Radian
+ * Degree : https://en.wikipedia.org/wiki/Degree_(angle)
+ *
+ * Angle in Radian = ( Angle in Degree ) x ( pi / 180 )
+ *
+ * Example :
+ * Question : Convert 90 degree to radian
+ * So, Angle in Degree = 90
+ *
+ * Solution :
+ * Angle in Radian = ( 90 ) x ( pi / 180 ) = pi / 2
+ *
+ * So, 90 degree is equal to pi / 2 radian
+ */
+
+/**
+ * @param {number} degree
+ * @return {number}
+ */
+export function degreeToRadian(degree) {
+  return degree * (Math.PI / 180)
+}

Maths/test/DegreeToRadian.test.js

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+import { degreeToRadian } from '../DegreeToRadian'
+
+test('should convert degree to radian:', () => {
+  const radianEqual = degreeToRadian(0)
+  expect(radianEqual).toBe(0)
+})
+
+test('should convert degree to radian:', () => {
+  const radianEqual = degreeToRadian(45)
+  expect(radianEqual).toBe(Math.PI / 4)
+})
+
+test('should convert degree to radian:', () => {
+  const radianEqual = degreeToRadian(90)
+  expect(radianEqual).toBe(Math.PI / 2)
+})
+
+test('should convert degree to radian:', () => {
+  const radianEqual = degreeToRadian(180)
+  expect(radianEqual).toBe(Math.PI)
+})