Add 'swapElements' function

[turisap]

Hi Kent, great course!

This is my first attempt to contribute, so I'd like to implement swapElements() function which would swap two given elements in an array. Please let me know if this can be done.

[kentcdodds]

Awesome! That sounds like a great contribution 👍

[kentcdodds]

Good job on #152!

[turisap]

Thank you Kent for a great opportunity to learn how to contribute!