Advanced version of the temp converter using 'this' and 'onkeydown'
There is another way to trigger events without using buttons, by
using onkeydown! So how do we know which element triggered the event?
By the 'this' keyword! This JS is still a little advanced for where
the class is at, but if you want to have a feel for where the class
is going next, take a look at the code and see if you can figure out
how it works!