test: Missing description fixed

Author: terkelg

test/average.test.js

@@ -1,7 +1,7 @@
 import { average } from '../src/math-toolbox'
 
 describe('Calculate average', () => {
-  it('', () => {
+  it('Expect the everage of 10, 10, 10, 20, 30 to be 16', () => {
     expect(average(10, 20, 10, 10, 30)).toBe(16)
   })
 })