Implement BMI calculation function and add test cases

Author: HadiVahidi20

Sprint-2/3-mandatory-implement/1-bmi.js

@@ -16,4 +16,7 @@
 
 function calculateBMI(weight, height) {
     // return the BMI of someone based off their weight and height
-}
+    return (weight / (height * height)).toFixed(1);
+}
+console.log(calculateBMI(70, 1.73));
+console.assert(calculateBMI(80, 1.73) === '26.7');