Added calculateBMI() implementation and test case using example values to verify output

Author: Eugenie-A

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

@@ -16,4 +16,8 @@
 
 function calculateBMI(weight, height) {
     // return the BMI of someone based off their weight and height
-}
+    return (weight / (height * height)).toFixed(1);  // toFixed(1) rounds to 1 decimal place.
+}
+
+// Test case
+console.log(calculateBMI(70, 1.73)) // Output: 23.4