algorithm: find length of an arc and area of the sector formed by an arc of a circle (#1119)

* Add an algorithm to find length and area of an arc of a circle

* Updated to follow Javascript Standard Style

* Update CircularArc.js

* Update CircularArc.js

* Add tests

* Followed Javascript standard style

Maths/test/CircularArc.test.js

@@ -0,0 +1,19 @@
+import { circularArcLength, circularArcArea } from '../CircularArc'
+
+describe('circularArcLength', () => {
+  it('with natural number', () => {
+    const arcLengthOfOneThirty = circularArcLength(1, 30)
+    const arcLengthOfThreeSixty = circularArcLength(3, 60)
+    expect(arcLengthOfOneThirty).toBe(0.5235987755982988)
+    expect(arcLengthOfThreeSixty).toBe(3.141592653589793)
+  })
+})
+
+describe('circularArcArea', () => {
+  it('with natural number', () => {
+    const arcAreaOfOneThirty = circularArcArea(1, 30)
+    const arcAreaOfThreeSixty = circularArcArea(3, 60)
+    expect(arcAreaOfOneThirty).toBe(0.2617993877991494)
+    expect(arcAreaOfThreeSixty).toBe(4.71238898038469)
+  })
+})